Probably have to have one custom made in order to match the contour of the barrel. Most aftermarket breaks thread onto a 5/8 x 24tpi threaded muzzle and are usually in between .8 and .9 inches in diameter. I used to have a miculek compensator on my Axis SR in 308 before I rebuilt it. If you search the forum you'll find threads with the companies that do custom breaks.

This topic has come up at least 5 times in the last month.