http://puu.sh/bztki/984e957d86.jpg here's a screenshot for reference. From my understanding the standard issue M1A1 Thompson had a 20 round box magazine. The 50 round drum magazine was made famous 20 years earlier by Al Capone's crew in Chicago but I don't recall seeing one in an accurate WWII context. My question is how did a grunt on Guadalcanal get a round drum for his standard issue Thompson? Please feel free to correct any misunderstandings I have on the matter.
It doesn't seem to be a M1A1 Thompson. In fact, if you look at the muzzle, it's much larger and doesn't cut when the M1A1 muzzle would. Instead, we see the Cutts compensator (which was there to decrease the muzzle climb) which is usually found in the M1921AC Thompson (as well as the M1928 Thompson).
