Your best bet is sell your barrel and buy one in the length you want. Talked to a buddy who makes carbon barrels and “most of the time” it’s not possible. Really depends on the barrel profile under the carbon.
You are over thinking this. Give it a good snug, stake it(if you so chose) and forget about it.
If you aren’t mechanically inclined and don’t know what properly snugged is for this part, just take it somewhere. Don’t buy a torque wrench just for this
Someone fit a new safety and hit it with a file 1 too many strokes it sounds like. There is a fine line between a properly fitter safety and one that doesn’t work.
It will not thread it because the major diameter is too big. Chuck it up in a drill and put some 400 grit to it. Measure until you get .210. I think it starts at .216.
I remember now. Its actual thread is a .210x28.
I think I got a 12-28 bolt and turned the diameter down to .210. Then cut two slits on each side to catch any debris. It was a good little project but worked perfectly. You aren’t going to find a tap in the correct size
I can do it if you want. I’ve done several for friends and several of my own. I think I only have 36 grit. It’s fairly aggressive but it’s great for a hot sweaty summer match day