Barrel floating? tang? scope rings tight? rings to base tight? base to receiver tight, all have torque values. rings 18-20 in/lbs ring to base 40 in/lbs. base to receiver I don't remember.
action screws depend on the stock and wether or not it has pillars.
Sporter barrel could be heating up if shooting fast-let it cool.
try different loads and/or bullets if reloading.
Lots and lots of variables to try.