I think that I asked something similar in the past and don't think I understood the answer, so, will try again. Can a standard mauser action accommodate, say, a 416 rigby? If, so, what model should I look for? i have Ball's book on the Mauser and If it answers the question I don't see it.

Yeah..it's been kicked around a lot: basically, the tea leaves say it's been done and can be done, but current wisdom suggests an overall cartridge length of 3.60 MAX. CIP specs call for a longer OAL, though Hornaday holds to 3.6...same as 300/375H&H...you might look up the pros and cons on ealier postings

Will a standard military mauser accommodate the 3.6 or larger oal?

To build a 416 on a mauser action that is safe and reliable you need a magnum mauser action which is very expensive. I have in the past made magnum actions from std actions by cutting out a section of one action and cutting and welding it onto another std. action than welded the first action together to make a mauser short action. The bolt has to be cut and welded as well and so does the firing pin, and floor plate. I quite doing it because of the time it took to do it right.

IF I were to try this, I'd use a commercial FN action.

instead of gambeling with your own or others health. You would be better of doing what koginam suggest.

If the cut on the actions is placed apx 1/4" different, you could end up with a safe solution, and 2 functioning actions. 1 Magnum, and 1 short.

Another thing, How mutch do you have to widening the magazine, and the sideramps, to make a 416 stack and feed properly, still maintaining an acceptable magazinecapacity.

By widening enough, you ought to get 4+1 in without any belley?

You've probably already heard this but, It's cheaper and easier to buy a CZ 550 in .416 R than to do what you are thinking of. You could then send it to AHR and have them install both their trigger and three position safety, slick up the action and still come out money ahead with a safe, modern action.

Thanks I did not think of a cz. There is a gunshow in Dallas next weekend and was going to look for a donor rifle