For those, like me, who didn’t know about the Grendel P-30 well now you do.

George Kellgren designed the Grendel P-30 back in 1990. It is a 20 oz pistol chambered in .22 WMR. It is the predecessor to the Kel-Tec PMR-30

The P-30 isnt the only predecessor. Kellgren also designed a carbine version. Like the RMR-30, the Grendel R-31 is the rifle chambered in .22WMR. Here is the only video I could find of one firing.