yes it is stamped sheet metal to make it cheap and easy to mass produce, remember it was developed in the 1940's. No, the military variant does not shoot .22 rimfire, it does however shoot a 230 grain .45 ACP slug at a velocity of around 900 FPS. so yeah A'den ur about right. It fires in one of 2 modes, semi or full automatic. I have not heard of Army cooks still using it, the services... i mean "force support" guys in the AF are issued M9s or M16s when they deploy, but we generally contract out to the locals for that kind of work in theater, the Army may work differently. It was a highly reliable but heavy piece of kit. Most everybody in the US military carries some variation on the M16/M4 series now a days. Yeah, sorry about the encyclopedia militaria answer there...lol but it's what I do.
Kal