I'm certain it would entail a re-barrel and the bolt face would be wrong, since the short magnum has a larger case head. The magazine would be set up for the fatter round also. Basically, it could be done I suppose, but I don't think it would be economical.
What Andy said!! In fact, you can open a bolt face, but I don't know how you could "close" it, so the conversion is essentially impossible if I am correct. Suggestion: buy the 270 WSM, load it way down, to the low end of 270 territory, and be happy. The difference between .277 and .264 is small indeed. BTW, I recently bought a used Winchester 70 in .300 WSM. Either mine has had a trigger job or Winchester makes the best factory triggers.
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