There isn't really an explanation based in reality as base dice 1s do the same thing and aren't related to ammo expenditure at all. From a pure game mechanics point of view, it's the risk you take for pushing a roll when lots of dice are in the dice pool. On average it will correlate with higher rates of fire but not always. For those times when it doesn't you could explain it as dirt in the breach or something.Not really relevant, but can anyone explain why firing 3 rounds (three "ones") as opposed to 18 rounds (three "sixes") decreases the reliability of a firearm when pushing? I'm legitimately asking cause I'm having a hard time interpreting this to my players.