Get real, you will never find one load and bullet that will group well in three different weight barrels, you won't find one that will group well in three identical rifles.
Better not tell that to competion BR or highpower shooters. If you peruse the loads used by the winners you will often find the same powders, almost identical charges, and the same bullet weights. Really. This was extremely comon in the 80s and 90s in BR where everyone used within 0.2 grains of the same charge of H322. HighPower shooters used to use charges within 0.5 grains of the same powder, usually IMR4895 and 168-grain bullets. This was because the rifles
really were identical - all were built with minimum chamber and bore dimensions, the same weight barrels, and were perfectly bedded. In those instances, identical loads really
did give the best accuracy in hundreds of rifles.
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