CP - I'd suggest you have one of the good double gun mechanics/smiths/makers vet your gun. Personally, I don't get the warm and fuzzies with guns that have had the chambers lengthened, especially for magnum loads. Long chambers do not make an old gun suitable for modern higher pressure loads for which it was not designed. The good news is that the action is more likely to be knocked off-face from excessive pressure or the stock crack from excessive recoil rather than the barrels burst.
With due respect to AM, I'm not a fan of do-it-yourself proof. The value in proof is skill in pre and post firing viewing to determine that no metal was permanently deformed. Unless this is accurately done, you run the risk of having damaged the gun during your high pressure firing and not know it.
