Jerry,
That is not going to work out very well if you try it. First of all you would have to find someone who already had a 12 gauge rifling head for their rifling machine. Second, your barrels are probably too thin to be thinking about rifling, there is just not that much wall thickness on your average upland bird gun. The best solution is to cut off the barrels at 2.5 to 3 inches in front of the breach. Bore them straight following their natural convergence, and make yourself up a mono block out of those barrels and sleeve in two rifled tubes.
You will then have to regulate it and put some ribs on it, all very doable and not that hard if you take your time and study out what you are doing. You will need a lathe or access to one, and possibly a machinist if you are not up to turning the barrel stubs.
At least if you do it this way you can have a gun that is regulated to shoot two shots to the same point of aim, is strong enough to do the job, and capable of having rifle sights added to it. If you need barrels or a top rib, contact me and I'll set you up with the parts. Bob H.
