Originally Posted by elkkillinfull
Ya I was using the same rest both times. I'm going to make sure the action screws are tight and take a look at the stock. And I am going to move .010 towards the lands and see what happens.
Also take a good hard look at the muzzle of the weapon and think about a flat base bullet. Most of the time when a load does this it's a boat-tail and a non-perfect muzzle combining to yaw the bullet a bit. With a cartridge as fast as the rum, it often doesn't show up at 100 yards. By 200 yards, the bullet has settled down and they are veering on their separate ways.
I'd try seating depth changes first, and maybe a powder switch to h1000 or rl22 to get the muzzle pressure down to get the yaw down. If that won't work, switch to either a flat base or a bullet such as the nosler offerings with a more moderate tail.
Possibly a lighter weight bullet is in order too. In my 7 rum I shot the 140 sierra(the 140 a-bond worked too) with 95 rl25 and a 215 in rem brass to 3.650". I also used the 175 hornady fb with I 5010 and rem brass with a 215.