Possibly insane moment, so ....
The MPA comes with a thread protector for the muzzle. I silver solder that inside a tube on one end. The other end would consist of someone's chopped off shotgun barrel that's already threaded for chokes, also silver soldered. I'd also use a brake cylinder hone to remove any "step" in the transition from the thread protector to the section with the choke. Effectively, I end up with this, without the need to touch my Hatsan's barrel:
http://www.brownells.com/gunsmith-t...s-gauges/screw-in-choke-adapter-prod7754.aspx
The MPA comes with a thread protector for the muzzle. I silver solder that inside a tube on one end. The other end would consist of someone's chopped off shotgun barrel that's already threaded for chokes, also silver soldered. I'd also use a brake cylinder hone to remove any "step" in the transition from the thread protector to the section with the choke. Effectively, I end up with this, without the need to touch my Hatsan's barrel:
http://www.brownells.com/gunsmith-t...s-gauges/screw-in-choke-adapter-prod7754.aspx