Odd things happened supply wise in the Pacific, I've seen photos of Marines with them in the past. Didn't really stop to think about it at the time. Where they got them would be interesting.

OSS also got some, dropped them with teams into Vietnam to help the Vietminh and some went into the ETO in weapons drops.

I've also seen photos of them in the field in the Phillipines during the liberation. They weren't common, but there were airborne forces there, and once again, odd supply things seem to have cropped up.

They were supposed to go to officers, heavy weapons crew, radiomen, etc in airborne and (I think) gliberborne units. Burgett mentions a friendly fire death owing to one in one of his books. Since the stock doesn't lock, it isn't the most useful thing. For those interested, Choate finally got the concept right in recent years.

M3 greaseguns weren't officially replaced for issue until the adoption of the M4 carbine. Some went with tankers to the Gulf War. Some are still in inventory in that tin foil looking paper stuff, usually with a mag pouch, couple mags, and I think you have to screw the barrel in. They were cheap to make and had a long service life.