I can appreciate where you are coming from. It is not so much keeping the barrel cool, it is minimizing the harmonic barrel vibrations caused by the bullet moving through the bore.
I understand where you are coming from with respect to using what you have on hand. That has been my approach in my quest to build a handicapped friendly rifle.
The greatest task you have at hand is making a sub moa rifle. Back before my accident, I shot a 24" barreled Remington 700 Varmint Special with a Weaver KT15 at 1000 yards. I was lazy and never really worked on making my hand loads better than 1 moa. At that time, I was loading Lake City Match cases with CCI BR2 primers, 40.5 gr of IMR4064 and the Sierra 175 gr MatchKing. That load generated about 2550 fps and held the 9 ring consistently when fired with a sling, not certain how that would shoot off a bipod or rest. I will start that load development in a few weeks as I build a new 308 thousand yard F class TR rifle. My AR platform rifle shoots well at 1000 yards, but becomes more marginal as I get close to sea level.
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