I don't think it's a warm barrel, unless your barrel is screwed up. This is the Mesa in 300 WM? You mentioned flyers earlier in the thread...I'm not insulting you here, but you may be flinching from recoil (or from muzzle blast if it's braked). I'd also recommend leaving the lead sled in the cabin and shooting off bags - one under the front, one under the back.
There are a myriad of things that could be happening with you, the rifle, the scope, the scope mounting. At 2-3" at 100 yards, you're probably a lot more average than the internet would lead you to believe.