I had Briley's in Texas perform a similar job on a fine old Merkel 16 bore gun that had the choke in the left tube removed for some reason and .009 remaining in the right tube. I wanted .020 choke in the left tube. Briley's purely botched the job in the beginning and I had to have them rework it twice, but I finally ended up with a nice job. I'll give them credit, they made it work to my detailed specifications, but not initially. They threaded the left tube, as for a removable choke tube, and FINALLY made me up a permanently installed custom turned choke tube that is now absolutely invisible inside and out. In the beginning they attempted to use an "off the shelf" .020 16 gauge tube, and it did not meet my instruction for an invisible job, due to the way they cut their choke tubes at the threaded end. It left a gap at the rear end that was very visible. Your minimum wall thickness is getting pretty thin, but if it is accurate a really good machinist might be able to thread it and use a permanent LocTite to keep it in. Mine has been fired quite a lot since the work a few years ago and I am happy now with the job. If you go this route, I would sugggest you insist on an invisible job, it can be done. I am not sure if your method of a slip-fit can be made permanent. Maybe. The threaded tube installation makes a good job. It will indeed require a very skilled machinist. Why not call Mike Orlen, if he is your choice, and discuss the job with him. If he doesn't want the job, try Briley's, but be very specific about what you want done. Lot'sa Luck!
