You are shooting 6.5...do they have on in the correct size for that?
308 brakes should work fine.
Coretac a local Canadian company makes specific RPR brakes and in 6.5C
http://www.coretacsolutions.com/products_CTS_RGPRMZ.htm
I may have to go with them, I had one a long time ago on a rifle sold. Loved how EZ they are to put on, but damn thing is a brick... I plan on hunting with this rifle, not sure I want a 50 cal sized brake on it.