your drilling the front trunnion rivets out and the inside rivet head never comes out?  ive drilled as far as i feel comfortable.  how do you know when the rivet head stops and the barrel starts?  also i used progressively larger drill bits until i got to the largest tap bit sized for 1/4-20.  then i tried using a flattened tap to try to start threads and i think i stripped it out.  so is there any hope for this one?

Push the barrel out and either rivet it or tap it with a plug tap with the barrel out.

Start with a plug tap you should get it started atleast then change to your bottom tap. I never got the rivets out of my kit after drilling so I tapped them, it gives 1-2 more threads. Look at the front side of the trunnion where the barrel comes out.....that thickness is how far you can drill. For the hole that is messed up you should just go with the next size tap and drill if needed and go again.