The 22 slide is a rim fire it's a 22 long rifle. Everything is the same on the bottom half (frame) of the gun you just slide it on put in the slide lock pin and a 22lr magazine and your ready to fire it is pretty neat. And shoots really accurate too. It took a few boxes to find some ammo it really likes, it seems to really like the regular lead roundnose ammo. Seems to jam on hollow points. I shot a golf ball size group with 20 rounds @ about 25ft standing not rested!