His gun wouldn't explode. Check out Demolition Range channel. The dude there had an episode where he was trying to curve bullet and even shot a rifle with a barrel bent the opposite way. Bullet will leave the barrel fine. It's just the barrel itself will break down much faster from the stress.
Also if the gun is jammed (not welded shut), it is very likely that bullet will push through and clear the barrel. On the same channel he abused some pistols jamming the barrel and trying to make them explode. It is surprising how resilient modern guns are.