I don't remember my father ever mentioning his use of shotguns during WWII, but they were around - he mentioned that "GI" 12 ga ammo used a full-length brass shell.
He did talk a bit about his use of shot cartridges in Thompson SMGs. He told me they were used for very close work in the densest jungle - a burst from one of them would "melt" the vegetation, as well as the Jap behind it. They worked fine up REAL close if you filled the entire mag with shot rounds, but if you tried to load magazines with alternating shot and ball to get a little bit more range, you'd get malfunctions.
I got the impression that after an inital burst of enthusiasm when they first got their hands on them, .45 shot rounds didn't find much favor with the GIs.
I have one cartridge he brought home - it looks pretty much like a round of "ball" ammo except where a normal 230 FMJ projectile would be there's an extended "dome" of red cardboard-like material; the shot is inside.
I *think* he mentioned another type of shot round that looked more like a slightly longer than average .45 case with a flat wad sealing the end . . . but my memory is a little hazy on that, and I don't have a sample.
