Even gentle twist rates in hunting rifles induce dizzying spins. A bullet rotating one turn every 12 inches at a velocity of 3,000 fps rotates 1,500 times in half a second and 400 yards of travel! In contrast, a V-6 engine pulling a pickup at 65 mph turns about 3,000 rpm. That’s 50 crankshaft rotations per second or just 25 per half-second.

Until recently, standard rifling twist rates worked for any hunting bullet because the heaviest were all blunt, thus no longer than lighter pointed bullets. Fast-twist barrels appeared for the .223 Rem. when shooters began using it at distance with long, sharp 60-, 70- then 80-grain match bullets. Standard 1-in-14 pitch gave way to rates as sharp as 1-in-7.5. Woodpecker-nosed 6.5mm-, 7mm- and .30-caliber bullets now crowd the starting line in races to claim the highest ballistic coefficient. The longest beg extra-fast spin. Bullet-makers and loading manuals have begun to note bullets that call faster-than-factory rifling twist. If you plan to use long bullets, check the specified twist of that new rifle before you buy it, lest you find those bullets spraying pie-plate groups — or perforating 100-yard targets sideways.