I just did a little tech research & found out the cheap metal handguns described above were called
The Liberator.
GM & a few other CONUS based plants cranked out these pistols so fighters & Allied troops supporters in denied areas(behind enemy lines) could pop a cap & grab a bad guy's SMG or rifle.
I've heard stories of Russians attacking enemy troops en masse then grab the rifle or weapon. The Chi-Coms did it to US/UN forces in South Korea too.
ClydeFrog