I have looked into these also, and was very serious in buying some, but from all the reviews I have read, I figured all I would be doing is wasting my money. I have read that they have a lot of hangups and problems. Apparently they do fit, but work? Not so much.... Just my two cents
I have 3 metal ones and thay work just fine, thay are marked (remington cal. 30-06, 308, 270 and 260.) I've owned 2 oter plastic ones and thay was junk. Thay fit but thats about it.
Is your rifle a semi auto? Bear in mind the remington 760/7600 is a fine HUNTING rifle, but the semi autos are only rated to 400 rounds. After that they pretty much fall apart. 400 rounds doesn't sound like a lot, but if all you use it for is to hunt once a year it is good for a couple lifetimes. I have a slide action (pump) 7600 and love it for deer, elk and bear.