M10

In looking for information regarding head-separation in pistol rounds, one forum's discussion contained a reference to "Lage uppers", apparently an upper for M10 (aka MAC-10) and M11 machine pistols.  Those guns are some of the cheapest MGs one can get, probably because of the cheap sheetmetal construction and the high rate-of-fire that makes them difficult to control.  The strength of the Lage uppers, then, is that they reduce the ROF from over 1000 RPM to 600 RPM.

I hadn't realized that the M10s had "upper" and "lower" halves, like an AR-15—that has me wondering if the registered part is the lower.  If so, that would make the gun more attractive, since the non-firing part is unlikely to wear out (except for the mount points of the upper).  Very interesting, except that those aren't C&R yet, and thus aren't legal in MN.  The only cheap C&R MG that I've found is the H&R Reising.