I'm it has been done, especially the 458 but the 375 is just a poor idea. To stretch the mag long enough a lot of the lower lug recess backing is removed and the top side of the receiver must be notched to allow unloading of unfired rounds. The later, high bynered Springfields and A3/A4's are fine as far as strength goes.. If the action is not been sporterised it is reaching the point where it's almost too valueable to cut up. Usually a commercial rifle in the caliber desired can be found for less money than a chop would entail..