A friend set up a NEF .410 for his girl for deer hunting. He drilled and tapped the receiver, put a scope mount and a red dot. It turned out well, and she's deadly with it. I considered doing the same with a NEF 20 gauge, having more power. After comparing the two, I noticed the .410 has .300 in. of steel thickness in the receiver, while the 20 ga. has .200 in. My question is what amount of thickness is required to be safe after drilling to keep the chamber from blowing up, and how deep do the threads need to be? I am a skilled machinist so I am capable, but not sure of the pressure capabilities of the round.