Mountain Billy Gun Lab's GOAT-15 runs on this proprietary 22 LR magazine, engineered for the GOAT-15 Helium, GOAT-15 H2, and GOAT-15 ATOM. Rimfire feeding is the make or break of any 22 platform - the rimmed case punishes sloppy magazine geometry - and the magazine built for the rifle is the one that gets it right.Keeping a few loaded magazines staged turns a range session into steady shooting instead of steady thumb work.