twist rate | Air gun blog - Pyramyd Air Report

Another twist on rifling

Posted on August 2, 2013 by B.B. Pelletier ↓ 52 Comments

by Tom Gaylord, a.k.a. B.B. Pelletier

I thought I’d provide some thoughts on how this blog has helped me become a better shooter. We just finished the Twist-rate test last week, and I wanted to share with you some things from that test that have impacted my shooting.

Swaged bullets
I’ve been using the output of the test to guide my own shooting with both firearms and airguns. I did test the swaged bullets in my muzzleloader already, but I discovered that there’s a lot more to learn. I can’t get the bullets I’ve swaged to group at 50 yards to save my life! I get maybe 1 out of 3 shots to land on paper. I think the problem is that I’m driving them too fast. I’ve been using the same load of black powder that I use for a patched ball, which seems like double the amount needed to get good results. When these bullets are fired in airguns, they’re shot at between 400 and 650 f.p.s., and I’ve been launching them at 1,000 to 1,200 f.p.s. I think I’m blowing them apart!

How does rifling twist rate affect velocity and/or accuracy? Part 13

Posted on July 24, 2013 by B.B. Pelletier ↓ 33 Comments

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8
Part 9
Part 10
Part 11
Part 12

This is the summary report in this series. I’ll give you my thoughts on how this test went, and I expect you to comment, as well.

The barrels
Three barrels were used in this test. One was the factory barrel that comes with the .22-caliber AirForce Talon SS. It’s a 12-inch Lothar Walther barrel that has a choke of about a half-thousandth inch reduction in the bore diameter for the final 2 inches of length. That makes all the pellets of uniform size as they leave the muzzle, and it may potentially stop any in-bore wobble. This barrel has the standard airgun twist rate of 1-turn-in-16-inches of bore travel, written as 1:16″.

How does rifling twist rate affect velocity and/or accuracy: Part 12

Posted on July 9, 2013 by B.B. Pelletier ↓ 68 Comments

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8
Part 9
Part 10
Part 11

Today, I’ll report on the final test in this series. This isn’t the final report — just the final test, which is the barrel with the 1:12″ twist, shooting at 50 yards. Get ready to be surprised. I know I was!

I did this test on the same perfect day as the factory barrel that was reported last week in Part 10, and the weather was perfect most of the time. From time to time, there was a very slight breeze that I waited out before shooting. The shooting conditions were as good as they get.

Changing barrels took 5 minutes. The silver barrel has the 1:12″ twist.

How does rifling twist rate affect velocity and/or accuracy? Part 11

Posted on July 3, 2013 by B.B. Pelletier ↓ 41 Comments

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8
Part 9
Part 10

Continuing our look at the 3 different twist-rates, today I’ll shoot the factory Lothar Walther barrel at 50 yards. The factory barrel has a 1:16″ twist rate that has become ubiquitous for airguns and is the very thing this test is designed to examine. Last time we looked at how the 1:22″ twist barrel did at 50 yards, with 2 different pellets fired at power levels 6 and 10. Today, we’ll see the same thing with the factory barrel.

This test was performed yesterday, and the range conditions were perfect. There wasn’t a breath of air to be felt for most of the shooting session, and only an occasional puff of air later on in the morning after I swapped barrels for the final test. I’ll report on that set of results in the next report. Today is devoted to the factory barrel.

How does rifling twist rate affect velocity and/or accuracy? Part 10

Posted on June 26, 2013 by B.B. Pelletier ↓ 39 Comments

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8
Part 9

Today, we’ll begin looking at the effects of the rifling twist rate on the accuracy of our test AirForce Talon SS rifle in .22 caliber at 50 yards. If you’re prone to jumping to conclusions before all the data is in, I have to caution you that today’s test will look bad because I’m testing the custom barrel that has the 1:22″ rifling twist. We know from the earlier tests that this barrel was most accurate at 10 meters on power levels zero and 6. Above that power level and also out at 25 yards, the accuracy of this twist rate broke down. So, it would be reasonable to assume that this barrel will give results that are even worse at 50 yards.

Rifling twist-rate primer: Part 1

Posted on June 20, 2013 by B.B. Pelletier ↓ 44 Comments

by Tom Gaylord, a.k.a. B.B. Pelletier

Recently, we have had a number of questions about rifling twist rates that were attached to the twist-rate report. These questions are extremely important to the understanding of how bullets and pellets are stabilized, so I’m starting a tutorial on rifling twists today. I’ll keep adding sections as I see the need to explain more about the topic.

Today, I want to lay a basic foundation of what the rifling twist rate does. Blog reader Feinwerk asked if centerfire rifles (he said higher-power firearm rifles) had different twist rates than rimfire rifles, and the answer is yes. I’ll get to that, but let me start at a time when things were much simpler.

How does rifling twist rate affect velocity and/or accuracy? Part 9

Posted on June 18, 2013 by B.B. Pelletier ↓ 42 Comments

by Tom Gaylord, a.k.a. B.B. Pelletier

Before we begin, there was a request last week for me to test the Benjamin 392. I thought I’d tested it already, and it turns out I did. Click see all 5 parts on the old blog.

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8

The question of barrel equivalency
Today, we’ll look at the accuracy side of this test, where yesterday we looked at how the twist rate affects velocity. Before I begin, however, we have to settle an issue that’s in a lot of people’s minds. Namely, is it reasonable to test barrels made by Dennis Quackenbush against a Lothar Walther factory AirForce barrel? Will the test results be skewed for that reason and not because of the different rifling twist rates? Or will the twist rates determine part of the results and the barrel’s pedigree determine the rest?