Just finished re-choking a Baikal O/U 12 ga. Tubes were cut down to 24", so I got it at a bargain(and the stock fits me perfectly!). Too thin to ream and thread, so I put a Imp-Mod choke tube on a mandrel, and turned it down to .75". Then I made a counterbore out of a .75" center drill, with about 2.5" of it ground down to the baikal bore diameter(.715-tight!). After boring back the top barrel, I glued the tube in with Loc-tite Hi Temp Sleeve and Bearing Retainer. Took it to the local trap range, and fired a 20 out of 25 on the second go round. Since it's been 18 tears since I shot trap, and the tube is still in, I consider the experiment a success. I will NOT try slugs in the top barrel, however! They shoot very well in the bottom barrel, still .715" cylinder. BTW, the Baikal tubes are hard chrome plated, so reaming/back boring didn't work for choking.

I have always wanted to Loctite 603 a barrel to a rifle with cylindrical surfaces with less than .008" clearance.

I have never got around to it.

But I have Silver soldered a .223 barrel to a Mauser barrel stub with cylindrical fit [ no threads].
It shoots ok.

I made a choke tube from 4140 steel and press fit it into a Charles Daly O/U .410 bore that had the chrome lining shot out of it. It worked very well.

Daly refused to honor their warranty and claimed I bought the gun used and I even had a sales receipt from Guns Unlimited in Omaha......