I have heard of numerous problems with the TC Katahdin bbl's in 460. Much of what I have heard is that the things are too light to start, and this causes horrendous recoil resulting in flinching among other problems. I am not suggesting that your flinching; however, the recoil does cause problems with mounts and scopes.
I have had several contenders and encores and had an encore rifle in 460 to hunt in the limited zone in Michigan. I no longer hunt in the limited zone. However, I came to the conclusion that weight is your friend if your going to go with the 460 in a rifle. Yes, as the above poster said, the 460 in a rifle is a monster, especially a light one. Especially if you shoot hot loads. I have seen where heavy hitters in the contender and encore snap screws in mounts and rings and forearms, the screws better be tight. The 460 likes to wreck scopes also (even after a few shots). I would recommend as stated above, get a steel base, ditch the shims. I like Warne rings, but if I was going with a stock encore (plastic stocks), I would get Badger Ordnance Rings, those are beasts, heavy and solid. If nothing else get a six screw mount from MGM, or I think Larry Kelly's outfit in Illinois used to sell them and/or mount them for you.
If still enamored with the 460 after messing around with the above, I would order a new bbl from MGM and get the full bull contour at 22 or 24'', then match it with laminated stocks from Boyds that also weigh a ton, put a big heavy scope on it of good quality, then you will have a beast, but you will thank me latter. That is the route I took after much horsing around, similar to your story. Yes you won't be stalking with such as gun, but if your sitting in a blind or stand all day, the weight won't matter. Recoil will be tolerable and you can wring out all that you want from the 460.
