The mainspring is a little weak on mine, but I've found that using plastic caps (as in cap pistol) instead of percussion caps will fire every time. Like the other fella' said, it's no tack driver, but it's fun to shoot.
BTW, I've loaded mine up to 30 to 40 grains of fff powder. There is substantially more recoil, but the barrel is the same strength as that of the .45 cal. rifles they make.