thats Aberdeen Proving grounds. I was there in the fall of 1963 and took the armys course on how to fix small arms we learned everything there is to know about M1 rifles, M14 rifles Browning 1919a4 air cooled Machine guns M1 Carbines, M60 machine guns, BARS, 3.5 rocket launchers, 81 mm,Mortors 4.2 Mortars, M@ .50 cal Machine guns 90mm and 106mm recoiless rifles and 1911a1 .45 auto pistols and last the M79 Grenade launcer the M16 was just out and the army had none. we got one on loan form the Air Force and learned only to field strip it on the last day of the course
APG proof of workmanship all of them, if you fixed it you fired it to prove that your work was good. we had a firing port to fire the rifles pistols and machine guns into. this is supposed to be a rule for all ordnance shops. how can you say you have fixed a weapon and given it back to the unit it came from and have it not work perhaps even in combat.
I bet that was cool. The only fun part of my MOS was when we got to do a few familiarity firings of the TOWs and Dragons.