Yeah I'll second the tough bullet selection if she's gonna use the 6mm. It will work, I prefer bigger as most do but I wouldn't necessarily buy a new rifle for one elk hunt. If she can handle and borrow something bigger though that would be my advice. Cup and core bullets in 6mm come apart very easily in my experience. They are fine for deer but it takes a good shot to put down an elk. I'd go bonded or Barnes TSX type of bullet as heavy as you can get.
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