I would go with a Classic post 64 action myself. For your uses a stainless one would be a plus. As far as functioning in extreme conditions I would say Mauser first and then it would be a toss up between Pre/Post 70 and Ruger 77. I might give a slight edge to the 70s due to the safety. The Nitride finish would just about eliminate the advantage of stainless, in fact better in my opinion. All of them will be comparable if finished out well after cycling the action for about a 1,000 times they will be similar in smoothness. Part of the reputation of the pre-64 smoothness is because most that you see have been cycled several thousand times as opposed to the newer M70s.

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