How does rifling twist rate affect velocity and/or accuracy? Part 3
by Tom Gaylord, a.k.a. B.B. Pelletier
This is a test of the effects of rifling twist rates on both the accuracy and velocity of pellets. I’m using a standard AirForce Talon SS rifle in .22 caliber and there are three barrels — each with a different twist rate. The factory Lothar Walther barrel has a 1:16 rate, and there are two barrels made by Dennis Quackenbush. The one we already tested has a 1:22 twist, and today we’ll look at the velocity produced by the 1:12 twist barrel.
I used the velocities for the factory barrel from an earlier test in the last part, so today I’ll also test the factory barrel at the test settings and report those results, as well. Let’s get started.
Power setting 0
The factory barrel delivered an average 480 f.p.s. on setting zero with Crosman Premier pellets, and the range went from 468 to 502 f.p.s. The spread was 34 f.p.s., and the average energy was 6.96 foot-pounds.
JSB Exacts, which weigh 15.9 grains, averaged 469 f.p.s. from the factory barrel. They ranged from 440 to 492, for a spread of 52 f.p.s. At the average velocity, they produced 7.77 foot-pounds of energy.
Premiers averaged 452 f.p.s. on setting zero with the 1:12 twist barrel. They ranged from 422 to 478 f.p.s., which is 56 f.p.s. At the average velocity, they produced 6.49 foot pounds of energy.
JSB Exacts averaged 434 f.p.s. on power setting zero with the 1:12 barrel. The spread went from 407 to 450, which is 43 f.p.s. in total. At the average velocity, they produced 6.65 foot-pounds of energy.
Power setting 6
On setting 6, Premiers in the factory barrel averaged 818 f.p.s., with a range from 801 to 828. So, the spread was 27 f.p.s. At the average velocity, Premiers produced 21.25 foot-pounds of energy.
JSB pellets produced an average 794 f.p.s. in the factory barrel on power setting 6. They ranged from 780 to 807 f.p.s, so a spread of 27 f.p.s. At the average velocity they produced 22.26 foot-pounds of energy
On setting 6, Premiers in the 1:12 barrel averaged 777 f.p.s. with a range from 734 to 797. The spread was 63 f.p.s. At the average velocity, Premiers produced 19.17 foot-pounds of energy.
JSB pellets in the 1:12 barrel on setting 6 produced an average of 786 f.p.s. The range was from 763 to 804 f.p.s., for a total spread of 41 f.p.s. At the average speed, the energy was 21.82 foot-pounds.
Power setting 10
On setting 10, Premiers in the factory barrel averaged 849 f.p.s., with a range from 846 to 851. The spread was 5 f.p.s. At the average velocity, Premiers produced 22.89 foot-pounds of energy.
JSB pellets produced an average 829 f.p.s. in the factory barrel on power setting 10. They ranged from 825 to 831 f.p.s, so a spread of 6 f.p.s. At the average velocity, they produced 24.27 foot-pounds of energy.
On setting 10, Premiers in the 1:12 barrel averaged 846 f.p.s. with a range from 838 to 854. The spread was 16 f.p.s. At the average velocity, Premiers produced 22.73 foot-pounds of energy.
JSB pellets produced an average 830 f.p.s. in the 1:12 on power setting 10. They ranged from 824 to 839 f.p.s, so a spread of 15 f.p.s. At the average velocity, they produced 24.33 foot-pounds of energy.
First, I’ll note that the velocity didn’t change much when I tested the factory barrel with Premiers on the test settings, but it did change significantly when tested with JSB Exacts. That poses no problem for this test because the next report will be one with all three barrels compared, and for that one I’ll use the test data collected from actual testing with the factory barrel. So, the estimated velocities of the first test will be replaced by today’s data.
The second observation is that on the lower power settings the factory barrel produced higher velocities than the 1:12 barrel. But on power setting 10, the difference was much closer. I’ll have to look at the results of the 1:22 barrel; but as I recall, it was superior in the middle power range.
Next, I will put all the data together so we can analyze them. I want you to remember that this is just the first cut at testing these barrels. This is just to point us toward the directions we should explore.
Of course, the accuracy test that comes next will tell us more about each barrel, and that may reflect back on this velocity test.
If you find today’s data confusing, don’t be discouraged. When I put it together, it should make more sense.