Armies think Proficiency is something spontaneous, or like having perfect pitch. Instead, an army finds either a quick learner or someone bringing skills in from civilian life. It is the number of careful shots fired. Slow learners fire more shots and they just take a little more time to get to Proficiency, but get there they do. Armies consider it something associated with having a military elite profile. Rubbish. I have seen a thin, short, very myopic middle-aged woman at a pistol range make one little hole with her M1911 Colt .45 automatic pistol. At an outdoor range, I have seen a genuine blue-haired old lady, with glasses to match, make a disturbingly large number of holes in the black at a thousand (1000) yards.
Keep all the military at the range at slow-fire and eventually the whole lot will plod to Proficiency and shoot about as well as the snipers. The track record of Proficient civilians put in the army and thrust into live-fire is 1.5 shots per hit/kill. This is the Hermann Phenomenon, first observed over 200 years ago. The record is stable through astounding equipment changes, because it is something one learns on the Long Plod to Proficiency.