I’d have way more luck killing them with the carbine than with any of my handguns.
I can barely hit the side of a barn with a pistol, but am pretty spot on with a long gun.
That's why they were issued, to give officers and support troops something besides that .45. Most people can't hit anything with a pistol, the .30 carbine was a fairly hot pistol round and easier to hit with than the .45 for the average officer, artillery, cooks and other personnel who didn't need an M1 Garand but needed to shoot now and then.