When the M852 7.62 NATO match ammo with Sierra 168's came out, folks with barrels that barely shot them fast enough from 22 inch 1:12 twist barrels with tight bores in warm, thin-air weather at high elevations did OK at 1000 yards. They stayed supersonic all the way from muzzle to paper.
Same rifle and ammo lot in temperatures in the 30's at low elevations created a situation where the thick air slowed bullets down enough to go subsonic around 800 yards. Accuracy beyond that range was measured in feet, not inches. Been at the Nationals when folks unaware of this happening on cold mornings listening to them say four-letter words about the accuracy of that ammo; 'twasn't "nice," "good" or words of that ilk. I've heard that some folks had 1:10 twists in their M1A's 22 inch barrels and they had better luck with the same ammo in the same conditions; bullets were spun about 20% faster in RPM's.