As others have pointed out, not hard to do. targets all concentrated, no return fire, etc. Wouldn’t be hard at all.
I’m questioning whether his weaponry would’ve been up to it. Barrel overheating is a real factor, real fast, on rock and roll.
In his position, with two bumpfire weapons, I would expect him to shoot both dry and then reload. Cycling between them gives each one a short rest to cool. They will both get hot, but he didn't care about accuracy.