Corrected entry: After Potter mocks Hawkeye for not hitting anything, Hawkeye replies "You fired as many shots as I did". In fact, Potter fired seven shots, Hawkeye only five. On a side note, this also suggests that Hawkeye probably was supposed to fire seven times, but his weapon jammed after the fifth shot.
Corrected entry: Hawkeye is discharging his sidearm into the air. It seems to be an (45. cal.) M1911A1, which was the most popular officer's sidearm during the Korean war, but he only shoots 5 times before announcing that that's all his bullets. The M1911A1 had a 7 shot magazine. (Potter seemingly did shoot 7 times.) Even allowing for the fact that his gun might not be fully loaded, muzzle flash is visible only after the third shot. The first and last two have none.