[big al hunter]

Ok, after re-reading your post I see what you are wanting to discuss. I don't know how much of a difference there would have to be to cause noticeable group change. If the bore was off center more than a few thousandth of an inch I could see where the difference in expansion might cause stringing. But I would think it would be less than an out of square receiver would cause. I would be curious to see testing that included barrel wall thickness and centering of the bore as a factor.....what do you suppose the factory tolerances are for bore centering.