General

AR-15 Custom Build Guide – 2017 Edition

I’ve written my advice for first time buyers of AR-15’s before, and provided plenty of technical details for barrels, optics, triggers, and other topics. However, I’ve never put together a list of suggested parts for a ground-up build. To be honest, that was intentional.

My general advice for new buyers was, and continues to be, go out and buy something like a Colt OEM for less than $800 and make it yours. Even better, pick up a complete Colt 6720 right now for $899 and rock on.

Still, I get a lot of questions about assembling rifles from scratch and picking parts.
This guide is my answer. This post is only concerned about the rifle itself, and not optics or sights. I break it down into functional categories and budget lines. You will see that I tend to stick to a baseline build, and then change only a few parts as the budget goes up.

This guide is based upon what is available right now. I know there are plenty of cool new whiz bangs just over the horizon (I’m looking at you UBR 2.0), but that makes things too complicated. Maybe they’ll make it in the guide next year. Also, I am not including the cost of shipping, tools, or paying someone to do the assembly for you. This is purely based on the cost of the parts.

I’m sure there are people who would read this list and wouldn’t agree with me. That’s fine. This is ultimately what I would build for myself were I to start all over again and choose to go the parts-rifle path. What works for me doesn’t work for everyone. Some of the decisions I made were driven by the budget I constrained myself to. Other decisions were honestly a wash between different parts, so I just picked one that met my needs.

The General-Purpose Carbine


The general-purpose carbine (GPC) is for someone who needs “the one rifle.” It is fairly good at most things, while not being outstanding at anything. It is easy to carry, easy to shoot, accurate enough, and serves as a constant companion for everything from home defense to competition. For most people, this is the category they are looking for when it comes to a “SHTF” gun.

The Baseline

Price Point: $800-$1000

The baseline GPC consists of the bare bones components needed to get a reliably functioning weapon. The parts on the baseline are inexpensive, without being “cheap,” and still theoretically meet reliability standards. I say theoretically because when go for a parts-rifle frankengun assembled from different brands, there is just never a guarantee.

This a great first rifle for someone who is ignoring advice to just buy factory built uppers and lowers, as it allows plenty of room for expansion in the future.

Contrary to my own advice, I went with a free floated barrel and low profile gas block from the start. I probably could have saved some money by going with standard handguard furniture and triangle front sight on the front end, but the labor costs would be higher on assembly due to the required drilling and pinning. Those labor costs would negate any savings made on going with standard plastic hardware, so I just skipped it.

Estimated weight: 6.37 lbs 
Estimated Cost: $894.39

Lower Receiver:

  • Stripped lower from Aero Precision
  • Daniel Defense LPK
  • Basic mil-spec trigger (included in the lower parts kit)
  • A2 pistol grip (included in LPK)
  • Standard safety selector (included in LPK)
  • Magpul MOE trigger guard (included in LPK)
  • BCM buffer tube
  • BCM carbine spring
  • H2 buffer
  • Magpul MOE carbine stock

Upper Receiver:

  • Aero Precision assembled flat top upper
  • 16” Faxon Gunner barrel
  • Faxon low-profile gas block
  • Standard mid-length gas tube
  • A2 “birdcage” flash hider and crush wafer
  • Aero Precision BCG
  • ALG EMR V3 13″ M-Lok handguard (and barrel nut)
  • BCM Mod4 charging handle

The Custom

Price Point: $1000-$1500

At the “custom” level, we can add a few more options that improve the shooting characteristics of the rifle. Changes from the baseline to the custom category include a Criterion barrel, known for high accuracy with chrome lining, a Centurion Arms handguard, A5 buffer kit, and a two-stage trigger (among other components). I also switched to a BCM M4 upper receiver because they are known for tight machining tolerances, particularly around the barrel extension, and help contribute to accuracy. The change from an Aero BCG to a BCM BCG came about mostly because I trust BCMs QC methods, as they individually test every bolt.

Estimated weight: 6.28 lbs
Estimated cost: $1303.17

Lower:

  • Aero Precision stripped lower
  • BCM Intermediate Buffer Tube (A5 Compatible)
  • Mil-Spec rifle buffer spring
  • Vltor A5H0 buffer
  • Sionics “Builder” lower parts kit (minus ambi safety selector)
  • V Seven Short throw safety selector
  • Larue MBT Trigger
  • BCM Gunfighter Stock
  • Hogue Overmold pistol grip (without grooves)

Upper:

  • BCM M4 flat top upper receiver (assembled)
  • Criterion 16” light hybrid barrel, sold through Midwest Industries
  • Faxon low profile gas block
  • Standard mid-length gas tube
  • Centurion Arms CMR M-Lok handguard (and barrel nut)
  • BCM M-16 Bolt Carrier
  • BCM Mod4 charging handle
  • A2 flash hider

The Unlimited

Price Point $1500-$2000

At the “Unlimited” level, we are looking to push the shooting characteristics of the gun to the best that can be expected of the general purpose carbine category. If funds are unlimited, and local politics allow, this is a great point to dip into NFA territory with suppressors and 14.5” barrels. For now, though, I will stay away from that and keep to keeping it NFA-friendly territory.

The goal is to continue pushing for more durable and accurate components while keeping weight down. With the unlimited category, I brought in matched billet receivers from CMT. These include several innovative ambidextrous features for magazine release and bolt stop. I switched to a Centurion Arms barrel, which is made from a different blend of steel, and known for both good accuracy and great durability. For the rail, I moved to a BAD 13.7″ Rigidrail, due to its very light weight while keeping rigidity. For a trigger, I brought in a Geissele SD-C. To be honest, my Larue MBT and Geissele SD-E are so close that another trigger upgrade is optional here.

To be honest, I had trouble pushing the budget much past the $1700 point. I could have spent another couple hundred on a lightweight billet set from Battle Arms Development or 2A Armament, but neither of them have the ambidextrous features that I think are valuable in this style of weapon. I could have also switched stocks to something more expensive, but at what point am I just picking more expensive parts for the sake of spending more money?

Estimated Weight: 6.54 lbs
Estimated Cost: $1897.13

Lower Receiver:

  • CMT Tactical Billet Ambi
  • BCM Intermediate Buffer Tube (A5 Compatible)
  • Sprinco ‘Green’ buffer spring
  • Vltor A5H0 buffer
  • Sionics “Builder” lower parts kit (minus ambi safety selector)
  • V Seven Short throw safety selector
  • Geissele SD-C trigger
  • BCM Gunfighter Stock
  • Hogue Overmold pistol grip (without grooves)

Upper Receiver:

  • CMT Billet receiver
  • Centurion Arms 16″ CHF lightweight
  • Centurion pinned low profile gas block
  • Standard mid-length gas tube
  • V Seven 13.5″ Enlightened M-Lok handguard (with barrel nut)
  • BCM M-16 Bolt Carrier
  • Geissele ambi charging handle
  • Precision Armament AFAB compensator (and shim kit)

The Field Rifle


The field rifle is one that will be carried mainly in open outdoors. It is at home slung across your back as you climb over rocky terrain, or slung up while lining up for a shot on a coyote. It is light and balanced, with a minimum of fuss. It can be pushed into service for defense of the home, but it is longer than a carbine built for the purpose. While not at the highest level of precision, it is more accurate than most shooters and will work well on all but the smallest targets out to the practical limits of the 5.56 cartridge.

My priorities for a field rifle are stability, balance, and velocity. Since this rifle is not intended for indoors or vehicle use, it is longer. It may be slightly heavier, but the weight is balanced to offset it. I’ll stick with the Magpul MOE rifle stock for all three levels because it is rigid, provides good cheek weld, and makes for a great overall feel on a field rifle. Your mileage, of course, may vary.

The Baseline

Price Point: $800-$1000

At the baseline, the field rifle looks similar to the GPC, except that it is slightly longer to take advantage of added velocity. Keeping to a budget will force decisions like that. The primary goal is to remain lightweight and easy to carry, but feel more substantial and confidence-inspiring in the hand. This will come mainly through paying attention to how the rifle balances.

Estimated Weight: 6.62 lbs
Estimated Cost: $969.32

Lower Receiver:

  • Stripped lower from Aero Precision
  • BCM Enhanced LPK
  • BCM PNT (included in the lower parts kit)
  • BCM pistol grip (included in LPK)
  • Standard safety selector (included in LPK)
  • Magpul MOE trigger guard (included in LPK)
  • BCM rifle buffer tube
  • Standard rifle buffer spring
  • Standard rifle buffer
  • Magpul MOE rifle stock

Upper Receiver:

  • Aero Precision assembled flat top upper without forward assist
  • 18” Faxon Gunner barrel
  • Faxon low-profile gas block
  • Standard rifle-length gas tube
  • BCM Gunfighter Mod 0 compensator
  • Aero Precision BCG
  • ALG EMR V3 15″ M-Lok handguard (and barrel nut)
  • BCM Mod4 charging handle

The Custom

Price Point: $1000 – $1500

With some extra funds, we can increase the accuracy and balance characteristics of the rifle. I happen to prefer a slight forward balance on a field rifle, since it helps the rifle settle into my hand and reduce sway from field positions. As with the general purpose carbine, I will make some adjustments to parts choices for the sake of tolerances and accuracy. The biggest adjustments will come from the barrel and trigger.

Estimated Weight: 7.2 lbs
Estimated Cost: $1377.72

Lower Receiver:

  • Stripped lower from Aero Precision
  • Sionics “Builder” LPK
  • Larue MBT Trigger
  • BCM pistol grip
  • V Seven short throw safety
  • Magpul MOE trigger guard
  • BCM rifle buffer tube
  • Standard rifle buffer spring
  • Standard rifle buffer
  • Magpul MOE rifle stock

Upper Receiver:

  • Rainier Arms non-forward assist upper
  • 17.7″ Ballistic Advantage Hanson profile 3-gun barrel
  • Ballistic Advantage pinned gas block (included with barrel)
  • Standard mid-length gas tube
  • BCM Gunfighter Mod 0 compensator
  • BCM BCG
  • Mega Arms Wedge-Lock M-Lok handguard (and barrel nut)
  • BCM Mod4 charging handle

The Unlimited

Price Point: $1500 – $2000

At the top end, we can take advantage of billet receivers and other higher end items. Overall, though, it retains the same basic style.

Estimated Weight: 7.4 lbs
Estimated Cost: $1905.80

Lower Receiver:

  • 2A Armament Balios Lite
  • Sionics “Builder” LPK
  • Geissele SD-E Trigger
  • BCM pistol grip
  • V Seven short throw safety
  • BCM rifle buffer tube
  • Standard rifle buffer spring
  • Standard rifle buffer
  • Magpul MOE rifle stock

Upper Receiver:

  • 2A Armament Balios Lite
  • 18″ Criterion Hybrid Profile barrel
  • BCM Low Profile gas block
  • Standard rifle-length gas tube
  • Precision Armament AFAB Compensator
  • BCM BCG
  • Mega Arms Wedge-Lock M-Lok handguard (and barrel nut)
  • Geissele charging handle

The Precision Shooter


This rifle is all about precision. It is at home on a bipod or a sandbag. It is heavy, a bit unwieldy, and not meant to be carried for long periods. It is ideally used in competition, but would serve very well for varmint shooting off the back of a truck. At all three levels here, I will use a longer barrel for the flattened trajectory, which is more useful to me.

From a precision standpoint, a more compact 16″ barrel would work just as well. Precision costs money, so there is increased cost at all levels.

The Baseline

Price point: $800-$1000

My priorities for this category of rifle are precision and stability. I also like a smooth cycle that helps keep sights on target for better shot calling.

Estimated Weight: 8.2 lbs
Estimated Cost: $961.89

Lower Receiver:

  • Stripped lower from Aero Precision
  • BCM Enhanced LPK
  • BCM PNT (included in the lower parts kit)
  • BCM pistol grip (included in LPK)
  • Standard safety selector (included in LPK)
  • Magpul MOE trigger guard (included in LPK)
  • BCM rifle buffer tube
  • Standard rifle buffer spring
  • Standard rifle buffer
  • Magpul MOE rifle stock

Upper Receiver:

  • Aero Precision assembled flat top upper without forward assist
  • Ballistic Advantage 20″ DMR Premium Series
  • Rainier Arms low-profile gas block
  • Standard rifle-length gas tube
  • A2 flash hider
  • Aero Precision BCG
  • ALG EMR V3 15″ M-Lok handguard (and barrel nut)
  • BCM Mod4 charging handle

The Custom

Price point: $1000- $1500

At the custom level, not much will change with the core rifle. We get the addition of a better trigger, adjustable stock, rail, and muzzle device.

Estimated Weight: 7.8 lbs
Estimated Cost: $1414.77

Lower Receiver:

  • Stripped lower from Aero Precision
  • BCM Enhanced LPK
  • Larue MBT Trigger
  • BCM pistol grip (included in LPK)
  • Standard safety selector (included in LPK)
  • Magpul MOE trigger guard (included in LPK)
  • BCM intermediate buffer tube
  • Sprinco “green” rifle spring
  • A5 buffer
  • BCM Gunfigher Mod 0 stock

Upper Receiver:

  • Aero Precision assembled flat top upper without forward assist
  • Ballistic Advantage 20″ DMR Premium Series
  • Rainier Arms low-profile gas block
  • Standard rifle-length gas tube
  • BCM Compensator
  • Aero Precision BCG
  • Mega Wedge-Lock M-Lok handguard (and barrel nut)
  • BCM Mod4 charging handle

The Unlimited

Price point: $1500-$2000

The unlimited level will change out the receivers, barrel, and a few operating parts. I’m sure there will be great debate over why I chose the parts I did, particularly the barrel, when there are known better ones out there. The answer is budget. To keep this below the $2k mark, I had to make some sacrifices. The parts I picked will still perform very well while staying well below the extraordinary prices some folks are willing to pay in the precision game.

Remember, when it comes to precision, the rifle is less important than the optics you put on it and your own abilities.

Estimated Weight: 8 lbs
Estimated Cost: $1964.82

Lower Receiver:

  • Mega Arms Billet Lower
  • Sionics LPK
  • Geissele High-Speed DMR trigger
  • Hogue overmold grip without finger grooves
  • V Seven short throw safety
  • BCM intermediate buffer tube
  • Sprinco “Green” rifle spring
  • A5 buffer
  • BCM Gunfighter Mod 0 stock

Upper Receiver:

  • Mega Arms Billet Upper
  • Rainier Arms Ultramatch .223 Wylde 20″ barrel
  • Rainier Arms low-profile gas block
  • Standard rifle-length gas tube
  • Precision Armament AFAB compensator
  • Aero Precision BCG
  • Mega Arms Wedge Lock M-lok handguard (and barrel nut)
  • BCM Mod4 charging handle

Conclusion

This concludes my build sheets for this year. The AR-15 is an extremely versatile and popular platform. You can take any of the specs I laid out above and further tweak them, but I do think they give you a good solid base to start from with each category and price point.

Good luck!

General

AR-15 Guide for First Time Buyers, Ver 2.0

I decided it was time to revisit one of the most popular posts on this blog: my advice to first time AR-15 buyers.

For a variety of reasons, the AR-15 platform is now the best selling rifle platform in the United States. With that popularity comes competition for your money, and unless you know how this market works, you are very likely to waste money in the process of buying one for yourself. This guide is intended for folks who are relatively new to shooting and are looking through Google, message boards, and other places for help on what to buy. If you have plenty of experience shooting, you will still find this guide useful- but you will be able to skip some of the advice since you probably already have a good grasp of what you are looking for.

DSC_0855

Before getting on with it, I want to explain where I went wrong with my first AR-15 (pictured here). I purchased a stripped lower and immediately started scouring the internet for what I should do with it. Over the course of about 10 months, I purchased each part individually as well as the tools to assemble them. I built a $3,000 carbine that the internet would be proud of. It was a sleek, bad ass looking, SHTF-ready general purpose carbine. It made a fantastic range toy that impressed everyone around me. However, once I actually started using it in local three gun competitions, its shortcomings became immediately apparent to me and I knew it was going to cost me more money to do some things over again. I then built a second carbine taking things back to basics (as I will advocate here). After shooting with that for a bit, I went back to my first AR and rebuilt it using lessons learned from my actual usage.

This brings me to my two fundamental laws of purchasing gear:

  1. Let the mission dictate the configuration
  2. Buy Once, Cry once

Let me explain these.

Let the Mission Dictate the Configuration

As simple as it sounds, this is the most difficult law for people to grasp. The AR-15 is so customizable that most buyers will immediately begin tailoring it to some perceived need even before they fully understand how they are going to use it. It took me years to understand one fundamental truth: a very generic weapon will do reasonably well at just about any task the AR-15 can be used for. The more specialized you make an AR for any particular use, the worse it will perform at others.

The last thirty years have seen an explosion in the possible configurations of an AR. We’veQyFiZ gone from the classic M16A2, to the M16A4, the M4A1 Carbine, the Mk 12 SPR (and it’s shorter cousin, the Recce), the Mk 18 CQBR, and a myriad of others in between. As the internet has filled with pictures of each of these, and the warriors who carry them, there is a certain element of, “I want that!

This sentiment is understandable, these guns all look amazing and they all exist because they have proven useful and reliable. But here is what you have to keep in mind: these configurations all exist to serve as compliments to one another. The M16 series offers the best all-around ballistic performance on an open battlefield, but its extra length will be more difficult when moving in cramped spaces. The Mk 18 and its 10.5″ barrel are great in cramped spaces, but it produces skull-rattling concussion and loses a huge amount of velocity (which limits its effective range). The Recce and SPR fit more into an intermediate category, but their precision optics and stainless barrels make them more useful for precision and less useful for volume of fire (for more information about how barrel length and material affect performance, please read my post on barrels). Everything is a trade off. It’s not a big deal, though, if the taxpayers are buying your weapons for you and you have a squad to outfit with a variety of weapons to compliment each other. It’s a different story if you have to buy them yourself and it may be the only rifle available to you in times of need.

maxresdefaultWhat does this mean to you? As I said before, a generalized weapon (such as the M16 or M4A1) will do reasonably well at any task you throw at them. The specialized weapon configurations really only shine when put in the hands of a skilled and practiced user. Put another way, a NRA high-master shooter will still shoot a chrome-lined M16A2 better than the average joe will shoot a fully customized national match rifle. Special parts and configurations only matter when comparing two skilled users who can take advantage of the capability. If you are a new shooter, you have not gained the skill and experience to even know how you will be employing your weapon, much less take advantage of the nifty gizmos you want to attach to it.

So what do I recommend for a first time buyer? I’ll get to that in a minute.

Buy Once, Cry Once

Don’t be cheap. There is a lot of competition for your discretionary income, and that means there is a lot of marketing dollars spent to sway you to one product over another. One of the worst mistakes you can make is to listen to gun store lore that says Brand X is “just as good as” Brand Y even though it is significantly cheaper. There is no such thing as a free ride. Every reduction in price must be paired with some other reduction in cost to the manufacturer. Typically, these costs will appear in material selection, quality control procedures, manufacturer tolerances, or other areas. If you are interested in the components of a quality AR, please read this post on technical specs.

Like most things, there absolutely is a point of diminishing returns. In the AR world, that point starts at about $1400. In my opinion, the sweet spot is between $900 and that $1400, where you are getting very high quality weapons that you can depend on for protecting your life, your family’s life, and performing in competition. Am I saying that a $500 Model 1 AR is going to fall apart tomorrow? No, not at all. But I am saying that the methods the manufacturer took to get the price point that low could affect the reliability and long term durability of the rifle; and you would have no way of knowing it was a problem until it becomes one (and that usually happens imgresat the absolute worst moment). If you know this weapon is purely a range or hunting toy that you will not bet your life upon, then no problem. If, on the other hand, there is the slightest chance that you might need this weapon to function in a desperate moment- that extra few hundred dollars is cheap insurance.

This doesn’t just apply to rifles, either. I have seen many a shooter buy a cheap red dot sight only to have it break in a couple months. By the time they have bought their third replacement, they have spent as much money on those three optics as they would have spent buying one quality optic up front. If you think a component is worth having, then its worth buying a high quality one at the start. That quality component will last the life the weapon, and probably a couple weapons after it.

Recommendations

Now that I’ve discussed my guiding principles, lets discuss what your first AR should look like. First, you are going to start with a basic configuration that will serve pretty well at just about any task you might have. I suggest only buying a complete rifle, or buying a complete lower and upper separately. At this point, do not attempt to piece together a rifle one part at a time (as I did). You will end up spending more money than you think on tools and shipping. Even then, you don’t have the technical knowledge on properly assembling parts together (especially mounting barrels and checking headspace). Sure, you could take it to a local gunsmith- but unless they truly know what they are doing, you will always wonder if the job was really done right. In that instance, you might be tempted to blame poor performance on the gun rather than yourself. That attitude will only drive you to spend more money on gear rather than ammo and practice. Buying a properly assembled quality rifle up front means any shortcomings are probably yours rather than the weapon’s.

Once you have your new AR, I suggest only spending enough money to get it up to the status of “minimum capable” for whatever it is you want to do. Once there, spend the rest of your money on quality ammunition and some training. Shoot the thing so much that it becomes second nature to you. Compete with it in a variety of styles from CMP/High Power to USPSA. Burn out the barrel. Once you have gone down this route, it will become very obvious where you should spend your money to best suit your needs. By this point, you will have expended enough money in ammunition that the cost of the widget in question will seem….paltry.

All of that said, here is my basic “minimum capable” recommendation for first time buyers. I will discuss variations afterwards.

  • 16″ Lightweight mid-length chrome lined barrel with a fixed front sight base
  • Either plastic handguards (Magpul MOE, Standard Round, BCM) or a quality free floated rail
  • Quality collapsable stock, without being too fancy, containing a H2 carbine buffer and spring (alternatively, I’m a big fan of the VLTOR A5 system)
  • Quality pistol grip of choice
  • Quality (but not fancy) trigger. The fanciest I would suggest at this point would be an ALG ACT or BCM PNT
  • Quality rear sight, with or without adjustment (Magpul MBUS/MBUS Pro, LMT L8A, Daniel Defense A1.5, Larue Lt 103, or even a carry handle from BCM or Colt)
  • If you have the money to buy an optic at this time, then go ahead and grab one that suits your needs- just remember to buy quality (Aimpoint, Trijicon, ELCAN, Zeiss, etc.)
  • Bonus: If you plan on using the weapon for defensive purposes, then you really should mount a white light on it (InForce WML, Elzetta, Surefire, etc.) and learn how to use it properly (i.e., only use in momentary bursts of light)
  • Bonus: You should get a sling.

The rifles below are a selection of various configurations I’ve used that roughly meet the criteria I laid out. The closest two are the one on the top left and bottom right. The top left, with FDE furniture, was my second AR and built with all of the lessons learned from building the first rifle. The second rifle, on the bottom right, was the first iteration of my marksmanship training rifle; it was nearly identical to the FDE rifle except that it had a 20″ barrel and a different stock. That longer rifle is now the one on the top right. The only significant changes are the addition of a free float rail, a muzzle compensator, and a Trijicon TR24. I made these changes only after shooting the rifle for several thousand rounds in a variety of circumstances.

There are many quality manufacturers out there, and I don’t have time to go down the pro/con for each one of them. So, to be blunt, I suggest that your first AR-15 should come from Colt, BCM, Daniel Defense, or Sionics Weapon Systems. These manufacturers all follow a good spec and stick around the same price point. Going much below these manufacturers in price should cause you to ask questions about what was done to reduce costs. Going much above their prices (as with Noveske, KAC, LMT, and others) should make you question if you are paying for a name or features that you are unable to take advantage of. Again, don’t get me wrong, I’m not saying its impossible reduce costs without sacrificing quality (supply chain management is one method of doing so). But I am asking that you don’t play that game with your first rifle since you don’t know a lot about the marketplace.

How did I arrive at this spec?

What separates the first iteration of this guide from the new Version 2.0 is that I have softened my stance a bit on a few things- particularly handguard and stock selection. Let me briefly explain each of theelements, and why I chose them as suggestions for a first timer.

I said a 16″ lightweight chrome lined barrel with a mid-length gas system because I gas-systemsbelieve it will be the most versatile for most people getting started in shooting. Heavy barrels really only shine in applications with high volumes of fire or an increased need for precision over the course of long strings of fire. Neither of those describe the average newbie. I used to suggest a 20″ barrel as well, and it is still a very viable option, but I don’t want to limit folks who might start using the carbine indoors for defending home and hearth.

I still suggest starting with a fixed triangle front sight base as opposed to the new trend of low profile gas blocks and rail-mounted front sights. The traditional triangle post is the sturdiest front sight and gas block you can use. If something has enough force to damage it, then there was probably enough force to destroy the whole rifle along with it. The fixed front sight is useful for point shooting, and works great for times where speed is of the essence. If you decide down the line that you want to mount a longer rail, then you can pay $40 to have it shaved down, or do it yourself, and still have one of the toughest and most rugged gas blocks available.

DSC_0339I still suggest most people should start with plastic handguards, but I’ve come around on the subject. There are many free float handguards on the market that are lighter than even the classic plastic ones. While most newbies will not really be able to take advantage of the accuracy benefit inherent in free floated barrels, it will be there for them in the future once they have practiced enough. The caveat, of course, is that you should do your research and buy quality. I take no sides in the Keymod vs M-LOK debate (though I have been using keymod), both will do the job well enough.

I used to suggest a plain collapsable stock like a Magpul MOE or standard Colt. I’ve backed off of that and will now say to pick a quality stock of your choice. BCM makes a great one, and Magpul makes several options. I suggest collapsable to better suit various shooters’ body mechanics. I’m also a fan of fixed rifle stocks, such as the A1, A2, and Magpul MOE rifle. If your primary usage is outdoors or at the range, a fixed stock has a lot of benefits in durability and smoother functioning (due to the longer action spring). Just remember, if you go the rifle route, you will need a different spring and buffer system than the carbine recommendation I made earlier. It’s up to you to do the homework on weight vs capability and how it affects your weapon. Remember, you should always strive for the lightest component that meets your needs and maintains reliability.

190261When it comes to triggers, I fully understand the temptation to jump for a $200 Geissele or Wilson Combat. I run Geisseles in all of my rifles at this point. However, I will admit that I did that before I could really take advantage of it. I’ve been shooting quite a few rifles with the ACT and PNT triggers, and they are all actually quite nice. They serve as fantastic interim triggers while you decide what route you wish to go in the future: combat two stage, light single stage, or any other variation. Once, and if, you go the route of fancy trigger, you still have a quality backup trigger in the parts bin. If you wish to know more, here is a post all about AR triggers.

When it comes to optics, I used to only suggest red dot sights. However, I realize that RearQuarter1many folks might not have eyes made for irons and red dots anymore. Some folks already know they want to go with magnification. For red dots, stick to the Aimpoint CRO, PRO, or T2 series. The Trijicon MRO has been getting a lot of attention lately as well. For magnified optics, the options are wide and varied. I’m a fan of Trijicon ACOGS and the ELCAN Specter series, but there are many more out there. You’re going to have to do your homework. For a quick overview of the market, here are my thoughts on optic selection.

For bonus items, I mentioned white lights and slings. In my opinion, no defensive rifle should be without a white light. It follows rule #4, knowing your target and what is behind it. Without a light, you might just be shooting at shadowy figures that may or may not be family members. As far as slings go, there are a huge number on the market tailored for various needs. You need to decide if you need one to serve more as a shooting aid, a retention device, or just carrying the rifle in the field. Pick one that suits your desires.

The Final Word

As I stated at the beginning, a generalized carbine will perform well at just about any role that can be expected of an AR-15. The more you start specializing it through fancy barrels, triggers, optics, rails, stocks, and accessories, the worse it will perform at all the other roles you didn’t specialize for. More so, those specialized guns only make a difference in the hands of a skilled user.

Until you have developed the experience and skill, then you really don’t know how you will prefer to use the rifle and what you can do to make it better for you. Until then, it’s all just theory and trying to be cool on the internet. Don’t do what I did.

General

AR-15 Buying Guide: Barrels

If you skipped my general advice for a first AR15, my recommendation there was to start with a basic lightweight 16″ or 20″ chrome-lined gun with collapsable stock and fixed front sight (from a reputable manufacturer, of course). If this is your first AR, I implore you to go back and read that post. The following advice is geared towards those who have already made that commitment, and are looking for ways to improve what they already have. It’s still good information, though, in case you were curious.

This post summarizes just about everything I’ve learned about barrels over the years. Note, I am not an engineer, so I’ll be skipping past the engineer speak and focusing on the basic easy-to-understand principles.

First, let’s review my two basic laws of buying AR-15s and accessories:

1. Let the Mission Dictate Configuration

2. Buy Once, Cry Once

I will focus on four main considerations for buying a new barrel: Length, Material, Profile, and Rifling. I will also talk a bit about the gas system at the end. Remember, there is no such thing as a free lunch. Every decision comes with a compromise in some other area. The more specialized you make your rifle for a particular task, the less suited it becomes for others. This is why I always recommend first time buyers start with a “generalized” gun that can do a bit of everything pretty well, but will be outperformed in specific roles compared to specialized configurations in the hands of the same skilled shooters. 

Allow me to clarify that last sentence. If you are new to shooting, then you have not developed the skill to take advantage of special configurations. An NRA High Power shooter with a High Master classification shooting a bare bones chrome-lined M16A2 will still outscore any new shooter, even if that newbie has a tricked out match rifle. The tricked out rifle really only makes a difference between two skilled shooters.

Ok, let’s go…


Barrel Length: The Long and Short of it

The barrel is the heart of the gun. The physical principles of gun barrel function have not significantly changed since the origins of rifles and cannon. There must always be a combustion chamber, a charge, and a projectile. What has changed over the generations is the method by which ammunition is loaded and the manufacturing technology available to consistently produce high-performing barrels.

Generally, a longer barrel will add more velocity to a projectile at the cost of weight and handling; a shorter barrel will reduce weight and create a more compact, lighter, and better handling gun at the expense of velocity and increased muzzle blast. A projectile is driven down the length of a gun barrel by the pressure of expanding explosive gasses from the powder charge. The cartridge case is mechanically locked in place by the bolt lugs, which means the only direction the gas can expand is toward the muzzle. The more time you give that gas to expand (via longer barrel length), the more energy will be imparted to the projectile. Once the projectile leaves the muzzle, or “uncorks,” then the expanding gasses will vent to the outside atmosphere and the pressure inside the whole system drops back to normal. Whatever energy the bullet has when it uncorks from the muzzle is all that it is ever going to have, and that energy begins decreasing immediately after uncorking.

The shorter the barrel gets, the less time there is for the expanding gasses to impart energy to the bullet. If the barrel is sufficiently short, then the initial powder charge may not have even fully burned yet, resulting in much more violent release of gas upon uncorking (hence the brutal muzzle blast and sparking fragments from short barreled rifles).

barrel5

This chart (which I grabbed from a great article at the Small Arms Defense Journal) shows the bore pressure from expanding gasses at the moment of uncorking. Higher pressure equates to more blast and concussion, and potentially more pronounced muzzle movement.

Why does velocity matter? The short answer is better trajectory and terminal effect. Contrary to what you may have heard, longer barrels are not inherently more accurate than shorter barrels (actually, the reverse is true; shorter barrels are stiffer and less prone to “whip,” but this effect is minuscule and you should not worry about it). The accuracy potential of a barrel has much more to do with its manufacturing method and the quality control (QC) procedures of the manufacturer. Velocity (and, by extension, a longer barrel) provides a “flatter” ballistic trajectory. For a marksman, this translates to less holdover or sight adjustment between different ranges [see this post]. There are many other factors involved here, such as the aerodynamic ballistic coefficient of the bullet. But for now, let’s just simplify by saying longer barrels provide more starting velocity and energy for a given projectile.

In some calibers, particularly 5.56, velocity is also important for terminal effect. This means that the higher the velocity is, the better the bullet will damage the target. This is important for hunters or self defense minded shooters. The 5.56 is a relatively light projectile, and most bullet designs rely on velocity to cause sufficient tissue damage (either through tumbling or other effects, dependent on bullet construction). The lower the velocity dips, the less effective the bullet becomes.

To illustrate, here is another chart from the same article at the Small Arms Defense Journal. In this chart, you see the initial velocity on a tested M855 bullet from different barrel lengths. In order to keep things consistent, they used the same barrel and cut it down one inch at a time from 24″ to 5″. The red line indicates the velocity at which the bullet can no longer be expected to reliably provide terminal effect. Note how the longer barrel lengths impart a higher starting velocity. This increases the possible ranges at which the M855 will reliably perform on target.

Screen-shot-2012-06-05-at-1.59.51-AM

Remember, this chart is geared towards M855. There are a lot of other bullet designs out there that will have a different velocity requirement. Some designs are not velocity dependent at all, and you will find these very popular among shooters who rely on very short barreled weapons. However, the underlying principle remains the same: longer barrels increase the possible effective range of a bullet. I’m not saying that the 5.56 isn’t useful once it drops below a certain velocity threshold; but below a certain velocity, we’re just poking .22 holes in things rather than causing massive tissue damage. Still, poking .22 sized holes in a living target is still effective as long as that hole is put somewhere vital. If all you’re doing is poking holes in paper on a shooting range, then this doesn’t really affect you.

Let’s discuss the practicalities of specific barrel lengths.

20″ Barrels – Old Reliable

20″ Barrels are the old school workhorse of the AR world. The AR-15, and 5.56 cartridge (particularly M193 and M855, the most common surplus cartridges available), were designed around a 20″ barrel. I would go so far as to argue that the 20″ barrel, and its rifle length gas system, is the optimum length for recoil characteristics, service life, and terminal effect. The chart above demonstrates this quite well. Notice that the peak velocity occurs at 20″, and starts to level off (or drop off) at longer lengths. While some ammunition loadings may be optimized for shorter barrels, the 20″ provides the most consistent performance across the widest variety of loads.

In a discussion I read with a few gentlemen in special units in the military, they almost always say that they will never sacrifice velocity if they don’t have to. While the rest of the AR shooting community is obsessed with going smaller and smaller, professional users only go shorter due to mission considerations (working out of cramped vehicles, weight concerns, confined spaces, etc).

You, as a bona fide member of the civilian world will probably never find yourself kicking down doors, charging out of an armored HMMWV (Humvee), or dropping out the back of a perfectly good airplane with a full combat load. In all likelihood, the most action the average AR owner will see is the time that it takes them to take the rifle out of the safe, drive to the range, shoot it, and drive back home. Weight is simply not a concern, even if people really really want to imagine that it is. So why not start with the most reliable and easiest to shoot configuration?

The longer 20″ barrel has a bonus benefit to the marksmanship-oriented shooter. The bit of extra weight out front provides some forward balance. This “hang” off the end of the gun is useful for reducing the wobble zone and decreasing muzzle jump after the shot. I would argue that these are more valuable benefits to the average user than the ability to do a 1-5 drill in a fraction of a second faster by using a shorter and lighter gun.

While the 20″ barrel has partially fallen out of popularity in the last fifteen years, my personal unscientific observation is that it is making a resurgence. The chatter I’m seeing is that people have had their fill of shorter guns (or can’t get SBR for legal reasons), and are looking for something more interesting than another vanilla 16″ AR. A lot of them bought modern versions of the old 20″ as a fun toy, or a clone of a service rifle, but have found that they actually like shooting it more than most any other gun in the collection. That should tell you something.

16″ Barrel- The All-Rounder

The 16″ barrel is kind of an oddity, really. I sincerely believe the 16″ AR is the most common length because it is the shortest allowed length under the NFA of 1934. If people could get an unmolested 14.5″ barrel, the length on the M4 carbine, then that would probably be the most popular. But, since the NFA is in play, the 16″ is it.

That’s not a bad thing, though. The extra 1.5″ over 14.5″ does impart a bit of a velocity boost. Quite a few new 5.56 loadings are being optimized for performance in 16″ barrels. The 20″ will still do things better, but the potential gain of going longer might not be worth the extra length and weight penalties. When it comes to home defense, the loss of 4″ off the end of the barrel does make a difference in handling and moving around the house “tactically,” but it really isn’t that significant (especially with a collapsable stock).

While the 20″ may shoot a bit flatter, and push the maximal terminal velocity envelop just a bit further out (about 50 meters), the 16″ will work just fine at the most realistic distances the average shooter will be using it. If your focus is on self defense scenarios, you will most likely never be able to justify taking a shot beyond the practical range of a 16″ barrel.

As a reminder, just because a 5.56 bullet drops below a given velocity, it doesn’t render it ineffective, it’s just not as effective as it could be. The 20″ and 16″ are both equally capable of hitting targets at 500-700 yards. Because of it’s good balance between velocity, weight, and compactness, the 16″ makes a great all-round performer for the shooter who isn’t quite sure what they really want to do yet. This is why I suggested it in my recommendations for the first time buyer.

14.5″ Barrel – The ‘Mil Spec’

14.5″ gained popularity because of the M4 carbine. Like the 16″ barrel, it provides a good all-round balance between weight, compactness, and velocity (being very close to the 16″). The 14.5″ has gained popularity in the last several years despite the NFA restrictions because of the ability to permanently attach a muzzle device to the end of the barrel and bring the overall length back up to legal ground. However, I dislike this path because it severely limits the user from being able to experiment with different muzzle devices, rails, sights, or the other things that we like to swap out on occasion. If you really want to go the 14.5″ route, then you might as well file the NFA paperwork and get your stamp so you can play with even shorter/handier lengths.

18″ Barrel – The Special Purpose Barrel/Competitor

The 18″ barrel has gained a lot of popularity for two reasons: 1) It is the length found on the military Mk12 SPR and 2) It provides a nice balance of velocity to weight to recoil characteristics in competition.

The 18″ barrel usually retains the same rifle length gas system of the 20″ barrel (I’ll talk about this below), but loses the two inches of steel from the end of the gun. This usually saves valuable ounces of weight, and takes them from the place that most affects the handling of the rifle. This makes it very popular in the three-gun competition world, especially when everyone is running heavy stainless barrels.

As far as the SPR goes, the 18″ was a compromise in order to keep the length down when using a suppressor. From my reading, most of the guys who had the option ended up ditching the 18″ barrel and going down to 16″ (otherwise known as the RECCE configuration).

I think the 18″ sits in a nice balance of length, weight, and recoil. It will retain the smooth recoil impulse of the rifle length gas system, while having better velocity and “hang” than a 16″ gun. But this is not without tradeoffs (I’ll discuss this in the gas system section).

Short Barrels 10.5″, 11.5″, 12.5″ 

The Mk18 CQBR issued to “cool dudes” uses a 10.5″ barrel. BCM has a really good explanation as to why they went with a 11.5″ barrel for their signature SBR. And quite a few professionals I’ve talked to have all expressed a preference for 12.5″ when available due to the previously mentioned mantra of “never turn down velocity.” These will all be short, relatively light, and quite handy for moving quickly. But they will also all be very loud due to the aforementioned pressure issues with short barrels.

If you are looking into these barrel lengths, then take your pick. They all have similar terminal performance and are designed to function roughly the same practical ranges. As one military contractor put it, the bad guy isn’t going to know or care if he got shot with an 11.5″ or a 12.5″ gun.


Barrel Material, or, How I Learned to Shut Up and Love Chrome

With barrel material, you basically have two common options: Chrome Moly or Stainless Steel. There is a wide variety of different metallurgical alloys within those categories, as well as surface coatings (chrome, nitride, etc). Rather than dig into engineering, I’ll just simplify as much as I can.

Stainless Steel

Stainless barrels, despite common perception, are not inherently more accurate. They are desired for accurate shooting, though, because their wear characteristics are more consistent and they are easier to machine. A quality CMV barrel will start to see accuracy drop off at X number of rounds and then consistently lose accuracy after that point until it becomes unserviceable, a stainless barrel will last a bit longer than ‘X’ before starting to show accuracy degradation (which will then occur at a much faster rate). Even then, a well made stainless barrel will drop off from outstanding accuracy to “really good” accuracy and still outperform most chrome lined CMV barrels on the market. ADCO posted a pretty good torture test on a 11.5″ stainless barrel that demonstrates this characteristic.

Stainless barrels also show a marked improvement to corrosion resistance over the CMV metals, meaning that they will rarely be chrome lined. Because they do not need lining, small barrel manufacturers like to use stainless because they can machine the barrel and send it out, minimizing their supply chain. This lets them used the saved money towards better machining and QC practices, providing a more accurate barrel for the price.

However, nothing is free. Stainless barrels, due to their molecular structure, are not as “tough” as CMV barrels and are more prone to problems in harsh temperatures.

There are three common metal alloys used for stainless barrels: 410, 416, and 416R. 410 is the “hardest,” and probably the most desirable. Rather than rehash it, go check out this thread on M4C, it is very informative and quotes quite a few experts. The bottom line recommendations on buying a stainless barrel are:

  •  Avoid lightweight or thin profile stainless steel barrels. This recommendation is echoed from multiple barrel manufactures due to the potential issues with temper embrittlement in martensitic stainless steels. The thicker walls of a medium, heavy, or bull profile barrel will strengthen the barrel and make up for the shortcomings of 400-series stainless steels as a barrel steel.
  • Avoid standard 416 stainless steel barrels. 410 and 416R stainless steels both have a lower sulfur content, making them less prone to developing sulphide stringers which may result in catastrophic barrel failure.
  • If the rifle will never see freezing temperatures, 410 stainless steel will likely be your best option. 410 stainless steel has the lowest sulfur content of the three grades we discussed, and will be the least likely to develop sulphide stringers. Avoiding sub-zero temperatures and using a barrel of adequate thickness should also minimize the temper embrittlement issue.
  • If the rifle may see freezing temperatures, 416R stainless steel will likely be your best option. 416R stainless steel is rated for use at temperatures as low as -40 degrees Fahrenheit and has a lower sulfur content than standard 416 stainless steel. However, you should still ensure the barrel is of adequate thickness.

CMV Barrels

CMV refers to a general blend of chrome-moly vanadium. The mil-spec metal, and the and the expected standard, is 11595-E. Better quality barrels will be made from a 4150 blend, while more inexpensive barrels will be made from a 4140 blend. 4150 is stronger and more heat tolerant than 4140; but I would say that the average AR buyer is not going to push their gun hard enough to notice a difference (but that’s for you to decide). Remember, this is just a basic rundown. At least one of my barrels is made from a different alloy designed for light machine gun use, and therefore has better heat tolerance than even 4150.

Machined bare, without coating, CMV barrels are every bit as accurate as stainless. They can be machined and profiled thinner and suffer fewer problems relating to temperature. On the other hand, they are also more prone to corrosion and have a lower lifespan (though, being honest, the average AR buyer will probably never wear out their first barrel).

There’s not much else to add, because the real difference between CMV barrels and stainless comes down to the linings.

Protecting Linings

History makes a big deal about the lack of chrome on the original M16s during Vietnam. Chrome provides a protective layer in the chamber and bore that increases the life of the barrel and reduces risk of corrosion.

Common wisdom is that consistency is accuracy, and that chrome lining reduces the accuracy of a barrel because the thickness of the coating is not consistent all the way down the bore. That remains mostly true. These days, though, manufacturers have figured out how to still make very accurate barrels with chrome lining (Lothaen, of The New Rifleman, is experimenting with one of these barrels right now from Criterion). I have a barrel from Centurion Arms that is chrome lined, and it has proven to be a solid 1 MOA performer. For comparison, the standard spec for a military barrel is 3-4 MOA, and the spec on bolt action sniper rifles used to be 2 MOA.

Another, newer, treatment is nitro carburizing. You will see this called a lot of trademarked names: Melonite, Tenifer, Salt Bath Nitride, and others. It is a chemical surface conversion of steel to make it harder and more corrosion resistant. Perhaps even more so than chrome. The “wow” factor is that it does this while not affecting accuracy. On the surface, it seems like a good process. Being honest, though, I don’t know enough to say if it is the best way to produce a barrel just yet. There is some concern about the high temperatures the barrel must be heated to in order to complete the process. These temperatures, especially for stainless barrels, are high enough to undo some of the important stress relief work that helps maintain accuracy (this will be covered later).

What should you get?

My honest opinion is that 99% of users are best served by a CMV barrel from a reputable manufacturer. Either chrome lined or nitrided will do. Stainless has its place for expert users who really want to squeeze out that extra 1/2 MOA from a barrel made at a boutique shop (Krieger, Bartlein, Shilen, etc), but most people really don’t need it, nor are they capable of taking advantage of it. The issues with cold environmental temperatures might be too much of a trade off, especially for hunters located in northern latitudes stalking through mountains in the colder months of the year.

That said, if you absolutely need better than 1 MOA, and can follow the tips above about stainless, then go for stainless. Otherwise, get a good CMV in a profile that works for you.


The Skinny (and Fat) on Barrel Profiles

photo-34

These barrels represent a selection of Lothar Walther barrels in various profiles (heaviest to lightest) available from Spikes Tactical.

There is only a minor difference in mechanical accuracy between a lightweight and a heavy barrel. They will both put your first shots where you aim them. Though, as with barrel length, there are trade offs to be made between profiles.

When metal heats, it expands. The hotter the metal gets, the more it deforms. This deformation is what causes accuracy loss in hot barrels. If you get a barrel sufficiently hot, it also destroys the rifling and severely shortens the life of a barrel. The underlying question of barrel profile is how long can the barrel sustain fire without becoming overheated to the point of unacceptable accuracy loss or destruction. Part of that depends on your definition of “acceptable accuracy loss.” For a combat shooter, going from 2 MOA to 5 MOA is still roughly “minute of bad guy.” But for a precision shooter, a 3 MOA drop in accuracy means the difference between hitting or missing a small target a 300 meters.

Let the needs dictate the configuration.

Lighter barrels will save valuable ounces (or pounds) off the end of the weapon, making it ‘point’ faster and be less burdensome to carry. However, light barrels will heat up faster and begin losing accuracy sooner. The average AR owner will probably not shoot enough ammunition in a year, much less in a few minutes, to cause a lightweight barrel to overheat to the point of failure. It is important to note that while they may heat up faster, light barrels also cool down faster.

In short, lighter barrels are better for for rifles that will be carried a lot and see light to medium duty shooting schedules.

Heavier barrels heat slower, and therefore show less deformation over the same firing schedule as a light barrel. They also take longer to cool down due to the extra material serving as a heat sink. This equates to a heavier and more cumbersome weapon, but one that will retain its accuracy over a longer string of shots.

Put these two together, and you have the basics to understand the trade off. If you have a gun that will be carried a lot, and shot on occasion (such as in hunting, patrolling, or surviving the zombie apocalypse), it is probably more beneficial to have a lighter profile. The original M16 followed this pattern with its pencil profile barrel.

If the gun will spend most of its life sitting on a bench and/or need to keep tight groups over long strings of shots, such as in competition, then a heavier profile may be in order.

There is always a happy medium. There are a lot of interesting profiles out there, more than I really want to talk about here. I will say that I think the government profile (which is lightweight at the rear by the receiver, and heavier at the muzzle) is counterintuitive. But it’s readily available, and it works [Note: I have since written about the origin of this profile]. My preference for the average user would be a pencil profile all the way through (like the old M16A1) or a medium taper profile that starts heavier by the chamber and then thins out as it reaches the muzzle (such as Criterion’s Hybrid profile, or Faxon’s Gunner profile).

In any case, based upon your usage, choose the profile that makes the most sense for you. Most people are far better served by a lighter barrel over a heavy one.


The Basics of Rifling

barrel_rifling

Twist rate and rifling is a hot topic. The standard wisdom is that you want a 1/7 twist, which means the rifling makes one full turn every seven inches of barrel length. You will also see 1/8 twist (usually in boutique stainless barrels), and 1/9 (more common among inexpensive models). The original AR-15 had a 1/14 twist, which later become 1/12 in the M16. The M16A2 increased the twist rate to 1/7 in order to accommodate the longer tracer rounds.

Bullet twist is not necessarily matched to bullet weight; it is matched to the length of the bullet. Longer bullets for the caliber (77gr SMK, for instance) will perform better with faster twists. If the twist rate is too slow, the bullet will not be stabilized and will be very inaccurate. There is a train of thought that talks about “overstabilization” of lighter bullets in fast twist barrels. My research tends to show that this usually applies to thin-jacketed or unjacketed cast lead bullets that will tend to “explode” if there is too much rotational velocity. For most people shooting standard match or surplus ammunition, overstabilization is not a thing to worry about and you will be fine shooting lighter/smaller bullets in faster twist barrels.

In any case, 99% of AR shooters will be well served with a 1/8 or 1/7 twist.

There are two main types of rifling patterns: land & groove, and polygonal. There is a lot of marketing hype around the latter, with a lot of companies putting their own spin on it (Remington’s 5r and Shilen’s Ratchet Rifling, for instance). This refers to the shape of the section of the barrel that ‘grabs’ the bullet and guides it down the barrel.  Polygonal styles claim some advantages in velocity, barrel life, and ease of cleaning. But they are about the same in accuracy, which depending more on the manufacturer than anything else. Either works fine.

ratchetRifle

On the left is an example of traditional rifling, the right is Shilen’s ratchet rifling.

When it comes to producing rifling, there are three methods: cut, button, and hammer forging. Cutting is the oldest method, and works by cutting each groove of the bore one at a time over many passes. Krieger is one of the most well known makers of “cut rifle” barrels, and they have a great reputation for accuracy. Cut rifling produces the least amount of stress on the barrel during formation.

Button rifling is essentially pulling a cutting “plug” through the bore to form the grooves. This is a newer technique compared to cut rifling, and is also the mil-spec for the M16 family. Very accurate barrels can also be made using this method, Criterion is one of the bigger names in the business, but there are many others out there. Button rifling is the most popular method.

The third method, hammer forging, is the newest, being developed by the Germans in 1939 as a way to mass produce barrels. The manufacturer creates a mirror-image ‘negative’ of the bore they desire and inserts it into an oversized ‘blank.’ The machine then pounds the blank down to size around the ‘negative’ mandrel and produces the desired rifling pattern. There is a lot of marketing hype surrounding hammer forged barrels, so be wary. They can still be very good barrels (I have one), and the way the metal grain is compressed can produce a slightly stronger barrel, but they aren’t the end all be all. Be wary of marketing claims that hammer forged barrels are more accurate or possess some other magic voodoo that makes them worth more than other barrels. There are only a few hammer forging machines in the US. FNUSA has one, Daniel Defense has one, the Freedom Group (Remington/Bushmaster/etc) has one, and there might be one or two more floating around. Just about any hammer forged barrel you see on the market was probably made at one of these facilities.

An important factor to consider is stress on the barrel during manufacture. Each of these methods produces stress in the metal, with hammer forging and button rifling created far more than cutting. Part of the manufacturing process is to “stress relieve” the barrels. This is an important step, as poor stress relieving means the barrel will be far more reactive to temperature, and the heat deformation could be terrible for your accuracy. Despite this, don’t get wrapped up in rifling method. Buy from a quality manufacturer. When you buy a quality barrel, you’re not really paying for the rifling method. You are paying for the skill, polish, and QC methods used to ensure the barrel is free of deformations and defects that might negatively affect performance. BCM, Daniel Defense, Centurion Arms, Lothar Walther, Criterion, Krieger, Bartlein, and many others all make or sell great barrels. Pick a length, profile, and twist that suits your needs- let the manufacturer worry about how it’s made.

Realize that not all barrels are the same even if they came from the same factory. Facilities that mass produce barrels perform up to a contracted specification. For instance, if Company X contracts FNUSA to produce 5,000 barrels to a very tight tolerance and high accuracy demand, that barrel will be more expensive due to the extra care required and to make up lost costs due to out of spec rejects. If Company Y has a looser tolerance to spec, and a lower accuracy demand, then they will get a barrel that meets that looser specification (maybe even barrels that were rejects from Company X) and sell them at a lower price point. Keep this in mind whenever someone says, “But this one was made in the same factory as that one, and it’s $150 less!”


And Finally, Gas Systems

gas-systems

There are really two components that affect the gas system performance in an AR. First is the length of the gas tube itself. Longer gas lengths mean lower operating pressures, which translate to smoother recoil impulse and reduced parts wear (remember what I said about 20″ barrels having the smoothest operation? This is why). But the second part of it is the actual gas port hole that is drilled into the barrel.

387bf-ar15-gasimpingement

In order for the weapon to cycle the bolt and load a fresh cartridge, some of the expanding gas is bled off from bore. It does this through the gas port. If the hole is too large, then the operating pressure is increased and the action of the rifle is more violent. This may  lead to malfunctions and premature parts wear. If the port is too small, then not enough gas enters the system and induces malfunctions like short stroking. There is a delicate balance between the size of the gas port and the length of the gas system. Not only that, but barrel makers must account for the gas port slowly enlarging over the life of the barrel due to the erosion forces of hot gasses and debris.

Eugene stoner designed for about an optimum 7″ between the gas port and the muzzle. This distance allows sufficient dwell time for the bullet to pass the port (when some gas will enter the system) and allow pressure to build before the bullet uncorks and depressurizes the whole system. If the distance is shorter than 7″, then the gas port must be enlarged to allow more gas. If the distance is longer than 7″, then the gas port will be smaller in order to avoid overpressure.

On a 20″ barrel, the gas port is about 13″ up the barrel. On an M4 carbine (14.5″ barrel), it’s at about 7.” On a 16″ midlength, it’s at 9.” All of these are relatively optimized. But when we start getting into oddball barrel lengths like 10.5, 11.5, 12.5, or 18, things get more complicated. The shorter barrels (10.5, 11.5, 12.5) all use a 7″ carbine length gas system found on a 14.5″ barrel, but must use oversized gas ports to make up for the lost dwell time.

With an 18″ barrel using a rifle gas, the same is true. The gas port must be enlarged in order to make up for the two inches of lost dwell time. This has a side effect of making 18″ somewhat finicky about ammunition. Overall, an 18″ rifle gas barrel will still shoot very smooth, but probably not as smooth as a 20″ barrel since it needs a larger gas port. One company (Noveske) did come out with an “intermediate” length gas system for their 18″ barrels that would be optimum for the 18″ length, but it is fairly propriety and not widely available.

The bottom line is this: gas length is related to barrel length and gas port size. A quality manufacturer will have already engineered this out for you. If you buy quality (BUY ONCE, CRY ONCE!), then you don’t need to be overly concerned about this minutiae.


The End

If you read all of that, then I salute you. Hopefully I’ve given you at least a decent understanding of the considerations involved in buying a new barrel. Remember, based on what you read here, be honest about your needs and intended use and choose accordingly. Never sacrifice velocity if you don’t have to. Never add weight if you don’t need it. Buy from a quality manufacturer.

Last revised 26 Jun 2016