How many shims will it take to make the barrel clock? I'm guessing more than one, if it only needed one I would peen or swage the barrell shoulder to get .005 and put it together completely dry, not every barrel is 80 to 100 ft lbs. and the extractor would let you know if something was rotating by wear pattern or the bolt not closing. Some mausers only bear on the inner ring. If I could not do that I would have to set the whole barrel back but the problem maybe is going to be the chrome lined barrel if that's the case with your rifle. If you just want to shim it and shoot it that's fine, but I wouldn't want to leave a vintage rifle to some one else that at a later time does not recognize the alteration. I do not know how many jap rifles would have been armory re-barreled in the first place but the originality is already gone with the replacement barrel. What condition is the original barrel that was re-chambered in since it was removed, mite be better to work with that if you just want to shoot it a bit.