All I have is a Gamo CFX
I always have problems finding ammo the damn thing likes though. It doesn't load like most single-shot pellet guns I've seen. Instead of it being something like a break barrel, you cock it, then rotate the breach open and insert the round. I'm assuming that's why it's kinda finicky with ammo. It seems like high quality ammo, crap like Beeman and RWS are like a half millimeter too long, and when you rotate the breech closed, it squashes the back of the round, which probably murders velocity and accuracy.
Here's an RWS in it.
With cheap stuff like Crosman, I have the opposite problem though. Normal rounds will fit fine, but their tolerances are so crappy that anywhere from 1 in 10 to 1 in 100 (depending on the tin I get) pellets will be way too small.
Gotta buy a new scope too. Damn one I have on now loses zero anytime the gun takes a little jolt.
Gun itself shoots well though. If I didn't suck at shooting with ironsights, I'd wouldn't even bother with the scope.