This is a public open beta for the GSG Series of mp5 22lr rifles. (GSG-5, GSG-5 A, GSG-5 L, GSG-5 P, GSG-5 PK, GSG-522)
Only I have been able to test it on one kit so I’m not ready to do a full release till I get some more info on kit compatibility and user issues.

Kits can occasionally be found on gunbroker sub 100$.
It’s a two piece clamshell style receiver.
Just print and clip around the bolt assembly and barrel.