A gas system wouldn't cycle the action if the bullet failed to travel far enough down the bore. A direct blowback system would. I'm not certain if it would be louder that usual, or quieter than usual. On one hand, modern rounds are designed so that they expand to fit the rifling, so if the cartridge goes off with extremely insufficient force, then it would likely just slide out of the barrel when you tipped it forward. Alternately, a round might just come apart in the barrel. The recoil would definitely be reduced because recoil partially comes from how much energy is released when the charge goes off. If the charge is too weak to push the projectile out, then it will naturally shove you a lot less. Now as how to get a stopped round out of a barrel, well, I'd consult an expert for that.
I've never had a bullet get stuck on me before, so what would I know?