RH, you are correct. Heat will show stress which will open up groups.
I'll bet that the "heat on a light barrel is bad" mentality stems from the era when most all rifles were unbedded and wood stocked.
Let me ask you this. Is it possible that such stresses would be completely repeatable with just 2-3 cold barrel shots, the first shots always being very close to the same place until the group opened up and started wondering around from heat, or would it be more likely to always shoot a pattern of X MOA size, shots landing anywhere within that area from first to last?
I shot my 7mm-08 Montana ten shots over 10 days at close to 200 yards prone off a pack and got roughly 2.5" with factory ammo. Some of it was the gun and some me. I hope to improve that with hand loaded ammo and more trigger time.
