Mulligan only has a small chance to return ammo for missed shots, not missed critical shots. I think it'd be cool if black hammer manually reloaded to 4 rounds, but white nail only added 3 back to the clip. Also, if the hive disruptor perk is messed up, just exchange it for the penetrate Knights black wall. That'd be more useful anyway. I don't know what can really take 3 critical hits without dying that isn't immune to them. Wizards have a shield, Knights have a shield, crota is immune to crits. Etc Etc Sucks when you get two shots off, then a player nudges you, you flinch from boss damage, the boss teleports, or dies, and miss that third hit. For enemies it'd be useful for, like gatekeeper, they can't survive long enough. Due to RoF, I can only manage two crits before my whole fire team has killed it. And atheons crit spot is weirdly displaced, and oracles don't take critical damage so you're still better off with ice breaker.