Twists &​​​​​​​ Turns

Exploring Barrel Twist Rates for .224-Inch Bullets

- Mike Thomas

For some time, I had been curious as to the maximum weight and length of bullets that would shoot well in older centerfire .22s with bore twist rates of 1:12 and 1:14. Like many shooters, I never gave this subject any thought until the fast twist rate .22 barrels became popular during the past decade or so.

Contemporary shooting enthusiasts have seen much in the way of development with long and heavy .22 bullets. High ballistic coefficients (BCs) serve to lessen velocity loss and wind drift. Long bullets of 65 to 80 grains or heavier perform much better at extended distances than the traditional, short, lightweight varmint bullets that weigh from 40 to 55 grains.

While the long established “slow” .22-caliber twist rates of 1:12 or 1:14 are capable of providing excellent accuracy with light bullets, such twist rates are much too slow for even minimal accuracy expectations with modern heavyweight bullets. For these, twist rates of 1:7 to 1:9 are required. The faster twists generally offer a versatility unobtainable with the slow twist rates in that they can be the basis for fine accuracy not only with the modern, heavy bullets, but also with many of the lightweights.

When I ventured into AR-15s for the first time a few years ago, I worked with three Colts, all with 1:7 barrels. I didn’t intend to load light bullets for these rifles, but as a matter of interest, tried bullets as light as the Sierra 53-grain MatchKing. Surprisingly, accuracy was very good, as it also was with varmint bullets of 55 grains.