I couldn't count how many boxes of Federal bulk ammo I've shot in my single-six. On occasion I'd have a round that wouldn't fire. I've had that experience sometimes in my NAA mini revolver too. I've only recently been able to shoot Federal bulk in my 22/45 (since installing a new extractor) and after shooting an entire box, there were no failures to fire. I always assumed my failures to fire in the revolvers were due to lapses in quality control. But no big deal since they're so cheap.