Well, actually, Jayne just said that Vera needed oxygen "around her" to fire. He didn't specify that it had anything to do with the ammo, just the gun. It's in the future, so who knows what the inner mechanics of that rifle looked like. Maybe in a vacuum the barometric regulators that help correct projectile flight path for altitude or atmospheric composition and/or pressure on different worlds would get confused and feed bad info to the main trajectory processor and the gun might jam. (In another post, I mentioned that, as a lifelong Star Trek fan, I can rationalize anything. <img src="/images/graemlins/wink.gif" alt="" />)

What actually bothers me is that, with the rifle in the suit, Jayne couldn't realistically aim with any accuracy, yet their lives depended on him making a long shot with incredible precision. Bringing to bear my amazing skills at making up explanations, I'll just have to assume Vera had the ability to plug into some sort of HUD in Jayne's suit. <img src="/images/graemlins/wink.gif" alt="" />

Stay safe,
J.T.