I have a 660 Rem just like that and I use Federal Premium in 165 gr. I get really good accuracy with this factory load. My brother has the 600 Mohawk but I not sure what he's using in his.
Good luck with that fine little rifle. It kicks hard when you're shooting at paper but worth it when u have to start carring it hunting. I've swat down and shot off my knee and took deer over two hundred yds. with mine and hit where I aimed.