Okay, two things on the rifle. First, it wouldn’t be absent of ALL recoil, since mass leaving the gun would inherently result in recoil no matter if it’s a result of gunpowder or not. That’s kind of an “erm, actually”, but still. Second, and more importantly, it doesn’t matter if the gun itself is silent, there’d still be a noise as long as the bullet is traveling at supersonic speeds, which I highly doubt it isn’t.