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 a .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.