well let's see
If you consider that the folks that started building the custom mausers built them to take to Africa in chambers like the 416 Rigby, maybe you wouldn't want to start there, but for me they work very well. All that is necessary to build it to a magnum caliber is opening the feed rails and the bolt face and I would use cross bolts. Niether of these should cost an arm and a leg. He may have to have the magazine opened up a little, all though this shouldn't cost an arm and a leg either. Take a look at the recievers of the model 700 and model 70, if they aren't set up for the magnum caliber, they will need the same modifications. Let's break down the price for him and let him decide. A good VZ24 action is going for $45 at FAC. He already knows what he will spend for the barrel and the stock and accessories. To buy a model 700 0r 70 ot Model 77, he will spend at least $300-400.00. Sure he can sell the barrel and stock if he finds someone who wants them, we'll say he makes $150 off of both of them combined. He still has spend at a minumum of $100 more. Unless he was fortunate to find a reciever in the magnum class, he will still have to spend money to have them done. Anyway you look at it, he saves money going with the VZ24. if you agree with the men who have hunted deadly animals, the mauser type extractor is the only one to be caught in the woods with. Now, the Winchester and Ruger both use this type of extractor, but to get one of their recievers in good shape will cost a little more than the $400.00. Let him decide.