Well said, hot barrel's
this and the cost, are the reason I favor the 17 fireball, 17 hornet, .204 and humble .222, for varmints,
for a pure varmint cal the little 17 hornet is cheap to run, and big on performance.
From the additional info, the orginal poster 300 BLK, has given, and his desire to use factory, I think the .243 or 6mm rem, or perhaps the .260 or 6.5 CM, in that order are his best options.
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