Factory magtech 150 gr ammo fires 6 to 7 rds will start getting harder each time to open the bolt sometimes I have to hit it with my palm two or three times
If you let it cool does it go back to normal? Is there a-lot of powder residue on cases after shooting and extraction? Are primers showing pressure signs? Ever clean bolt and breach?
Just a second. Is it tight to close before shooting??
If not AND it happens with different ammo could be dirty chamber and or bolt recesses. You could buy a chamber brush for an ar-10 which will help get chamber and bolt recesses clean since your rifle is a 308win.
You might have a tight chamber. I have an older commercial mauser that has an absolutely min spec chamber. To the point several different types of ammo would be basically a crush fit to load. Any gun smith can check that for you.