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!

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4 thoughts on “AR-15 Custom Build Guide – 2017 Edition”

  1. Thanks for the awesome post. I was recently gifted a KAC RAS M5, a stripped upper, & a box of miscellaneous parts. I know you like the Faxon 18″ barrel (I will also be getting one soon) & I cannot find anyone that will pin a FSB on a nitrided barrel. I was hoping you could point me in the right direction so I could get my jack of all trades upper done. Also, any thoughts on the new Vortex 1-8x Strike Eagle?

    Thanks & keep your powder dry.

    1. Thanks for reading, I’m glad you enjoyed the post. As to your question regarding getting an FSB pinned on the Faxon, it does seem difficult to find someone willing to do the work.

      Before I left California, I had gotten quotes from both Rainier Arms and West Coast Armory to do the work. I ended up not sending it off because my move date was rapidly approaching and I didn’t want one more thing to keep tabs on during the move process, so I sat on it. Now that I’ve settled on the east coast, I was directed to WAR rifles in Manassas. I spoke to the owner, and he seems willing to do it for increased cost (melonite is hell on drill bits). I haven’t taken it over to him just yet, though.

      As far as the new 1-8 Strike Eagle goes, I honestly think its too new on the market to have an honest opinion. I certainly haven’t handled one, yet. That said, given its price point, it is on the lower end of the optic spectrum for Vortex. Functionally, it will do what it is supposed to do, but with a lower glass and build quality than something like the PST or Razor line. Depending on your intended uses, that might be fine. At that price point, I would also be considering offerings from Atibal and Primary Arms. But, if you need a bit more durability and clarity, I bet you could find some deals on used Gen I PST scopes, or even come back to a 1-6 or 1-4 and get great deals.

  2. Glad to see your move has been completed and your back to posting again!

    Whats with all the marksmanship oriented blogs moving across the country?

    Out of CA! Congrats!

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