CB caps might be OK, but so far all I've used is Colibri's or super Colibri's ( I've shot super Colibri's in I think all of my guns with no issues )
& never had a problem, & actually enjoy shooting them... I think if I was going to shoot alot in a weaker or older gun, I'd stick with the regular Colibri's
like this... ( I now have several bricks )
http://www.midwayusa.com/Find?userSearchQuery=colibri