Posts Tagged ‘Dennis Quackenbush’

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

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″.

The other 2 barrels were made by Dennis Quackenbush. Neither barrel is choked. One is a 1:12″ twist; the other is a 1:22″ twist. They’re also about 12-inches long and are held in the gun by AirForce Talon SS barrel bushings. Several comments have suggested that because these barrels are different than the Lothar Walther barrel, this test is somehow not fair. But the results of all the shooting prove otherwise. Sure, there are variations from barrel to barrel, depending on the power used and which pellet was shot. But the results are so close between all 3 barrels that whatever differences there might be are overridden by the similarities. In other words, I’m suggesting that if Lothar Walther had made all 3 barrels, there would be similar differences.

Talon SS precharged air rifle twist rate test 3 barrels
The 3 barrels used in the test. Factory barrel in the middle.

I believe the twist rates are what drive the results. We weren’t searching for the most accurate barrel in this test. We were looking for behavior changes as conditions were changed. And we got that.

Velocity
The first thing that was tested was velocity. Both pellets — the 14.3-grain Crosman Premiers and the 15.9-grain JSB Exact Jumbo were shot from all 3 barrels at each of 3 predetermined power settings. These settings were marked on the gun so they were kept constant throughout the test.

Talon SS power settings
The power settings were the power indicator screw all the way to the left (the lowest setting), and the power screw centered on each mark (settings 6 and 10).

 

07-24-13-01-Velocity-table

I reviewed the velocity for you in Part 8. Here’s a summary of that report.

In all cases, the velocity increased the most between power setting zero and setting 6. The velocity increase from setting 6 to setting 10 was always smaller than the increase from setting zero to setting 6, and that’s irrespective of the twist rate or which pellet was shot.

What you’re seeing here is the slowing down of the rate of velocity increase as the air flow increases. That’ll become clear in a moment when I discuss the rifle’s maximum velocity potential.

As the twist rate slowed (1:22″ is slower than 1:12″), the velocity increased at most power settings with most pellets. There was one instance with the 1:22″ barrel when the JSB Exact pellet actually went 2 f.p.s. slower at setting 10 than at setting 6; but with all other barrels and pellets, there was always a velocity increase as the power setting went higher.

Focusing on the 1:22″ barrel for a moment, we see that the velocity increases between setting 6 and setting 10 were not as great as they were in either the factory (1:16″) barrel or the 1:12″ barrel. This suggests what we have suspected all along — that the twist rate of the barrel does slow down the pellet as it gets tighter. And we can see from this test that the phenomenon is most apparent at the lower power settings. At the higher power settings, the differences seem to shrink, indicating that the influence of the power setting is overriding the influence of the twist rate. I believe this is an important finding, and it sets up the next observation, which is that the top velocity of the gun was fairly close for all 3 barrels, regardless of the twist rate. The type of pellet made more difference to the top velocity than the barrel twist rate did.

It should be obvious from these results that the Talon SS powerplant has upper limits that cannot be exceeded by forcing more compressed air through the barrel. This illustrates the relationship between barrel length and velocity in a pneumatic airgun.

A second thing I found interesting is that power setting 6 is very close in performance to power setting 10. In the case of the 1:22″ twist barrel, it’s remarkably close…but it’s close for all three barrels. A prudent airgunner might consider this when setting the power wheel adjustment on his Talon SS, knowing that a lower setting uses less air, yet gives velocity that isn’t that much slower.

A third thing is that the velocity performance of the 1:22″ barrel is so good at power setting 6 that it makes power setting 10 useless. Take that thought just a little farther, and you’ll see that all power settings above setting 10 are pretty much a waste of air in a Talon SS with a 12-inch barrel, regardless of which pellet you use.

Accuracy testing
Next, I tested all 3 barrels with both pellets shot at all 3 power levels at 10 meters (11 yards) and 25 yards. Following that, I tested all 3 barrels and both pellets, again, at 50 yards, only I didn’t use the zero power setting. This was where my eyes were opened regarding the effects of twist rate.

Accuracy table final

I analyzed the accuracy in 2 different reports. One (Part 9) was the 10-meter and 25-yard accuracy and the other (Part 12) was the 50-yard accuracy, alone. Now, with the table above we can combine these results and analyze all the accuracy data together.

The first observation I’ll make is that at 10 meters, I got 10-shot groups that ranged from as small as 0.092 inches to as large as 0.578 inches. The factory barrel gave the best results with the JSB pellet; but with the Premier, it was the 1:22-inch twist that did the best. Curiously, that pellet and twist rate didn’t seem to change that much as the power was increased (at 10 meters). With all other barrels and pellets, the group size did change a lot as the power changed.

It’s too simple to say the factory barrel with the 1:16-inch twist rate is the best; but of the 3 twist rates in this test, it certainly is the most flexible across the board. However, you’ll notice that the 1:12-inch twist barrel did shoot the best single group (with JSB Exact pellets) at 50 yards. That group is so close to the Crosman Premier group shot by the 1:16-inch barrel that I can’t call a clear winner — BUT — here is what I CAN say. The Quackenbush 1:12-inch twist barrel is certainly capable of shooting 50-yard groups at least as tight as those shot by the Lother Walther barrel; and in my mind, that puts the barrel-equivalency question to rest.

Another observation is that the 1:22-inch twist barrel was just as good at 10 meters as the other 2 barrels, in general, but look at how the groups opened at 50 yards! That says something very strong about the relationship of the twist rate to accuracy. And it also brings up a second observation.

Premier pellets and JSB pellets performed differently throughout this test. Just look at the 50-yard results for Premiers and JSBs with the 1:12-inch twist barrel, and you’ll see what I mean. This is one more bit of evidence that barrels have preferences for certain pellets.

Final observation
This will be my final remark in this series of reports, and it does not come from the data collected in this test but from the 5-part test of the Diana model 25 smoothbore. In that test, we saw that the smoothbore was able to place 10 JSB Exact RS pellets into a group measuring 0.337 inches at 10 meters. However, at 25 yards, the same pellet loaded the same way made a group that measured 3.168 inches. That difference tells us clearly that spin and not aerodynamic drag is the main key to pellet accuracy. I think we now see that twist rates do matter a lot, and the standard rate is the best all-around rate for now.

Diana 25 smoothbore JSB Exact RS deep-seated group
At 10 meters, 10 JSB Exact RS pellets made this 0.337-inch group.

Diana 25 smoothbore JSB Exact RS deep-seated group2 25 yards
At 25 yards, the same JWB-Exact-RS pellets, seated to the same depth, made this 3.168-inch group. They are clearly not accurate after 10 meters.

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

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.

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

I used the same two pellets we’ve been shooting all along, and they were shot at power settings 6 and 10…just like the other 2 barrels that went before. The gun was shot while resting on a sandbag that’s very stable. When the tank was filled or the power was changed, I always shot one shot to settle the valve. Experience tells me that’s all that’s needed.

AirForce Talon SS filling the tankThe tank was filled to 3,000 psi.

Power setting 10
I first shot both pellets on power setting 10. And 14.3-grain Crosman Premiers were hitting low and to the left. One of them only nicked the target paper, so I photographed the target before taking it off the backer paper, so you could see the complete group.

AirForce Talon SS Premier group still on target stand Here are the two 10-shot groups of Premiers. Notice that they’re hitting to the right of the aim point, which is the center of the bull they touch. The group shot on power setting 10 is at the top, and it shows why I like to use backer paper when shooting at 50 yards.

AirForce Talon SS Premier group 50 yards power 10 Premiers on power setting 10 gave this 2.577-inch group. See the nick on the right edge of the target paper? I had to guess a little for this measurement, but it isn’t too far off.

Then it was time to test the 15.9-grain JSB Exact Jumbo 15.9-grain pellet on power setting 10. This is where the surprise comes! Ten pellets made a 1.259-inch group! If you check back with the results the factory barrel gave, you’ll see that this group is very close to the best group made by the factory barrel (1.153″ for 10 shots with the same JSB pellet on power setting 6), and it’s equal to the group that was shot on power setting 10 (1.283″). This addresses a question many of have had from the beginning of this test — namely, are the Quackenbush barrels equal to the Lothar Walther barrel?

AirForce Talon JSB Jumbo group 50 yards power 10 JSB Jumbo 15.9-grain domes on power setting 10 gave this 1.259-inch group. This shows that the 1:12″ barrel can be accurate at 50 yards.

With so little data, it’s impossible to say if these two barrels are exactly as good, but what we now can say is that one of the Quackenbush barrels gave some groups that are at least equivalent to those from the factory barrel. The difference is so small that it might be due to the twist rate rather than the quality of the barrels. That was the position I took at the start of the test, and I think this demonstrates it was valid.

Power setting 6
Next, it was time to test the 1:12″ barrel on power setting 6. Ten Premiers went into 2.234 inches, which is only slightly smaller than the same pellet on power setting 10. As before, the pellet stuck the target low and to the right.

AirForce Talon Premier group 50 yards power 6 Ten Crosman Premiers on power setting 6 gave this 2.234-inch group. This is similar to the group that was obtained on power setting 10. The difference is too close to call.

It’s official — the 1:12″ barrel does not like Crosman Premiers out at 50 yards. But that wasn’t the only pellet in this test.

With JSB Exact Jumbo 15.9-grain domes, the barrel did nearly as good on power setting 6 as it did on setting 10. Ten pellets made a 1.363-inch group. Like the Premiers, the JSBs also performed about the same on setting 6 as on setting 10. But that’s not the real lesson. The real thing to note is that the 1:12″ twist barrel was not as good at 25 yards as the factory barrel, yet at 50 yards it almost caught up. In other words, the accuracy of the factory barrel degraded faster as the distance increased than the barrel with the faster twist.

AirForce Talon JSB Jumbo group 50 yards power 6 Ten JSB Exact domes on power setting 6 gave this 1.363-inch group. Like the Premiers, this result is also very similar to the group that was obtained with this pellet on power setting 10.

What has been learned?
This is not the final report. I’ll add these results to the previous summary report given in Part 9, and we’ll be able to see all 3 barrels at all 3 distances with both pellets at all 3 power levels. But if I had to give a quick analysis, I’d say the 1:12″ twist barrel surprised me at 50 yards by being better than I expected. At least it was better with the JSB pellets.

And that fact alone — that a barrel can be so much better with one pellet than with another — is good to know. This test has demonstrated that principle beyond all doubt.

A lot more testing needs to be done to thoroughly see all the relationships, but I’ll tell you what I know in the next report, which will be the final report for this series. I think we can advance our knowledge of how pellets perform by quite a bit by combining the results of this lengthy test, the smoothbore test and the pellet velocity versus accuracy test. We’ve been exploring this theme for nearly 2 full years now, and I think we’ve learned a lot!

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

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.

The AirForce Talon SS shoots with a fill of 3,000 psi, so before the test I filled the reservoir. Twenty shots would be fired at power setting 10 and another 20 at power setting 6, plus one shot at the start of the test and when the power wheel was changed. I haven’t reported that fact until now, but it’s my standard practice when shooting at 50 yards with a Talon SS.

Valve needs to be exercised
I have learned that the Talon SS valve needs to be fired one time following power adjustments to get it set at the new power level. The first shot will usually be like the gun was on the previous power setting, but the second shot will be solidly at the new setting; so I always take one shot to set the valve with every fill and at every power change.

Talon SS Tom at bench

Shooting off the bench at 50 yards on a perfect day with the Talon SS was enjoyable.

Power setting 10
I started with power setting 10; so when it was time to shoot on power setting 6, the reservoir would have less than the full fill pressure. That way, I knew the gun would be right in the middle of the power curve.

Crosman Premiers
The first pellets I tested were 14.3-grain Crosman Premiers. Because the groups had dropped so far below the aim point in the previous test with the 1:22″ barrel, I dialed up the elevation several clicks for this test. I was hoping to hit the bullseye with the new sight setting, but Premiers on power setting 10 still dropped about 3.50 inches at 50 yards. Ten Crosman Premiers went into a group measuring 1.567 inches between centers. While that’s on the large side for a Talon SS in my experience, it was still a very round group.

Talon SS Premiers 50 yards 10 power

At 50 yards, 10 Crosman Premiers went into this round group, which measures 1.567 inches between centers when the power was set to 10.

JSB Exact Jumbo
Next, I switched pellets to 15.9-grain JSB Exact Jumbo and shot another group of 10. This was also at power setting 10, so the gun’s valve did not need to be awakened. These pellets hit about 2.50 inches below the aim point, so they landed higher than Premiers at the same sight setting. This time, the 10 pellets went into 1.283 inches — a much better group than the Premiers, though there was a hint of vertical elongation to this group.

Talon SS JSB Exact Heavy 50 yards10 power

Ten JSB Exact Jumbo pellets made this 1.283-inch group at 50 yards on power setting 10. This group is slightly vertical.

The difference between the Premier group and the JSB group was evident through the scope without walking down to the target. Clearly this barrel likes the JSB pellet better. What did surprise me was that even on this perfect day I did not shoot a group smaller than one inch. I’ve done that so many times in the past that I sort of expected it — especially on such a perfect day. Well, it just demonstrates the difficulty of shooting such tight 10-shot groups at this distance.

Now, I cranked the power wheel down to 6 and shot both pellets, again. The first shot settled the valve at this new setting, then the groups began in earnest. JSBs went first since I’d just finished shooting them at power setting 10.

This time, 10 JSB pellets went into a group that measured 1.53 inches between centers. It was larger than the same pellets on power setting 10, but smaller than the Premiers on setting 10. The group is fairly round, though most of the shots are clustered on the right side.

Talon SS JSB Exact Heavy 50 yards 6 power

Ten JSB Exact Jumbo pellets made this 1.53-inch group at 50 yards on power setting 6. Notice that 7 of the 10 pellets landed on the right side of the group.

The final group was 10 Premiers fired on power setting 6. They made a group measuring 1.261 inches, which is the best group of the 4 shot with this barrel. It’s more open than the best group of JSB pellets, but the overall measurement places it at the top of the ladder.

Talon SS Premiers 50 yards 6 power
Ten Crosman Premiers on power setting 6 made the best group of the day, measuring 1.261 inches between centers.

Did you notice that the pellets crossed in their performance relative to power, with JSBs doing best on power setting 10, while Premiers did best on power setting 6? I wouldn’t make too much of that because we don’t have enough data to make any conclusions, but it is interesting. In the macro, it does appear that Premiers prefer lower power while JSBs prefer higher power — at least at 50 yards.

I have to admit that I was surprised not to see even one group that measured less than one inch. I’ve shot so many small groups with this rifle that I expected it this time, at least with one of the four groups that were produced.

Final note
In the next report, which is the same shooting done with the 1:12″ twist, there will be a surprising result. So, there’s still more to come.

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

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.

That didn’t stop me from trying my hardest to shoot well. I was able to watch each pellet go into the target paper because of the distance, and that was disconcerting when the pellets landed so far from the aim point and from each other. Let’s take a look at how the rifle did.

The day was nearly perfect, as it has to be to get good accuracy from pellets at 50 yards. The air was calm, except for some light breezes from time to time. I was able to work around these breezes and get the results I was after.

I decided not to test the rifle on zero power because of the long distance to the target. Any breeze would have so much time to blow the pellets off course that I felt it wouldn’t prove anything. So, both pellets were shot on power levels 6 and 10. That’s how I’ll test all 3 barrels.

You may remember that this barrel produced velocities that were very close to each other at power levels 6 and 10. With 14.3-grain Crosman Premiers, the respective velocities were 840/854 f.p.s.; and with 15.9-grain JSB Exact Jumbos, the velocities were 817/815 f.p.s. We expect the pellets in this test to go to the same place on the target, and I would expect the two groups for each pellet to be pretty similar in size.

Crosman Premiers
I started with Crosman Premiers and the power set to 10. I did not adjust the scope since completing the 25-yard accuracy test and the center of the group landed about 3.9 inches below the aim point. Ten pellets went into a group that measures 2.04 inches between centers.

Talon SS rifle Premiers 50 yards power 10
Ten Crosman Premiers went into 2.04 inches at 50 yards on power setting 10. The center of this group was about 3.90 inches below the aim point with the scope set for 25 yards. The pellet at the top center is part of another group — not this one. I did account for the full size of the pellet on the left that just clipped the edge of the target paper.

On power setting 6, the center of the group also struck the target 3.90 inches below the aim point. These measurements of the groups are just approximate since the center of each group was difficult to locate precisely. The 10-shot group size on power setting 6 was 2.607 inches between centers. This is slightly larger than the group shot on power setting 10.

Talon SS rifle Premiers 50 yards power 6
Ten Crosman Premiers went into 2.607 inches at 50 yards on power setting 6. The pellet hole at the lower right is not part of this group.

JSB Exact Jumbo
Next, it was time to test the JSB Exact Jumbo pellet. I started with power setting 10. The center of the group landed about 4.25 inches below the aim point.

Ten pellets shot on power setting 10 went into a group that measures 2.509 inches between centers. The group is much taller than it is wide.

Talon SS rifle JSB Heavys 50 yards power 10
Ten JSB Exact Jumbo pellets went into 2.509 inches at 50 yards on power setting 10. The group is taller than it is wide for reasons unknown.

On power setting 6, the 10-shot group size was 3.222 inches between centers. This group is considerably wider than the group shot on setting 10. Why that is, I have no idea.

Talon SS rifle JSB Heavys 50 yards power 6
Ten JSB Exact Jumbo pellets went into 3.222 inches at 50 yards on power setting 6. The group is quite a bit wider than the group shot on power setting 10. I have no idea why that is.

Conclusions
As expected, neither pellet did especially well at 50 yards with the 1:22″ twist barrel. They did stay closer together than I expected, however.

The Premiers were more accurate than the JSBs, which parallels what both pellets did at 25 yards.

I don’t see any real evidence of tumbling pellets with either pellet on either power setting, so it’s too simple to say they’re just destabilizing. They’re less accurate but still stable at this distance. There’s probably something profound in that — something like the pellets still fly point-forward, but erratically. I can’t prove anything, yet, but now I have one barrel’s results in the can and it’s time to look at the factory barrel next. And that one has the twist rate that the manufacturer thinks is best for this airgun.

Final note
When I pitched the idea for this test as a feature article for Shotgun News, the editor told me he has never seen a test like this before. Neither have I. This may, in fact, be the first time anyone has published the results of testing three rifled barrels of different twist rates in the same gun under the same conditions. It probably has applications in the firearms world as well as for airguns. So, you readers may be in on something that’s being done for the first time.

We still have to test the factory barrel and the 1:12″ twist barrel at 50 yards. As a final report, I’ll summarize the entire test and the lessons I believe it teaches us.

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

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?

To carry that kind of logic out to its conclusion, every barrel will be different. Who’s to say that one Lothar Walther barrel is not better or worse than another? The fact is that we know that some of them will stand apart — being either better or worse than the norm. There’s no way to test the exact same barrel with all 3 twist rates because we cannot adjust the twist rate of a rifled barrel. Once it’s built, it is whatever it is. Three separate barrels have to be used for this test, whether they’re made by Lothar Walther or by someone else.

Another thing to consider is that other smallbore barrels made by Dennis Quackenbush in the past have proven to be as accurate as barrels made by Lothar Walther. I’m now talking about barrels of the same caliber — not comparing .22-caliber Walther barrels against .308-caliber Quackenbush barrels. I know of .22-caliber barrels and .25-caliber barrels made by Quackenbush that can go against the best barrels made by Lothar Walther.

But in the end, we can never know if the barrels I’m using for this test are exactly as accurate as the Lothar Walther factory barrel I am also using. There is just no way to know that. There is, however, a way of getting pretty close. If the Quackenbush barrels produce some groups in the same accuracy range as the Lothar Walther barrel, then we can be assured that we are testing barrels of similar quality. We can never be entirely certain they are exactly as good, so this is as close as it is possible to come. And, by the same logic, that is all we could do if Lothar Walther had made all 3 barrels used in this test.

Lothar Walther is not going to make test barrels for a test like this unless they want to. There is no way to contract with them to make one-off barrels that have the different twist rates we are testing. They don’t make one-off barrels — at least not for the public. There are barrel makers who do make one-off barrels, and Dennis Quackenbush is one of them. We’re going to have to be satisfied with the barrels he has provided and look at the results to see if we believe his barrels are as good as the factory barrel we’re testing.

On with the test
With that issue set aside, let’s look at what the 3 barrels did in this test.

Rifling twist rate and accuracyThe group sizes in the table are shown in inches.

General observations
The first thing I looked at was the results of the 2 Quackenbush barrels against the factory Lothar Walther barrel, and I learned something interesting. At 10 meters, the 1:22″ twist barrel shot better than the factory barrel with Crosman Premier pellets — not by a little, but by a significant margin. On both zero and 6 power, the 1:22″ barrel made groups that were one-tenth of an inch smaller than those made by the factory barrel. On power setting 10, the factory barrel beat the 1:22″ barrel by only four one-hundredths of an inch. I think that’s significant. It shows that the 1:22″ twist barrel can keep up with and even exceed the Lothar Walther barrel…at least to 10 meters.

The 1:12″ twist barrel wasn’t quite as good as the factory barrel at 10 meters, but it was very close. At power settings zero and 6 they differed by just a few thousandths of an inch. On setting 10, the factory barrel exceeded the 1:12″ barrel by the same four one-hundredths of an inch that it did with the 1:22″ barrel.

These results tell me that the two barrels made by Dennis Quackenbush are as capable of making good groups as the Lothar Walther barrel. The differences in the group sizes are less than the measurement errors made when measuring the groups. That puts the barrel equivalency question to rest in my mind. I’m willing to accept that the results of this test are from the different twist rates and not from the inherent quality or lack of quality of the barrels being tested.

Ten meters is really too close for definitive results when the question of accuracy is on the line. That’s why the test was also shot at 25 yards, and later I’ll shoot it at 50 yards. It was at that distance that the factory barrel really shined. With 14.3-grain Crosman Premiers, the factory barrel was more accurate on power setting 10 than on the lower settings. With 15.9-grain JSB Exacts, the factory barrel did its best on power setting 6. But both of the other barrels did not perform their best at this range.

The 1:12″ barrel shot Crosman Premiers best on power setting 6, but it shot JSB Exacts about the same on settings 6 and 10. There was a little difference with the Exacts, but it was down in the measurement error margin.

The 1:22″ barrel, on the other hand, got worse with Premiers as the power was increased. And the difference between the best and worst groups was large enough to be more than a coincidence. It was almost twice as large on power setting 10 as it was on power setting zero (1.082″ compared to 0.671″).

With JSB Exact pellets, that trend was reversed. The greater the power, the smaller the groups became. For both pellets at 25 yards, the 1:22″ barrel was not anywhere near the factory barrel at the same distance. Only at power setting zero with Premiers was that barrel close to the factory barrel, and the difference was still outside the measuring-error margin.

The 1:12″ barrel performed similar to the 1:22″ barrel at 25 yards. Only once, at power setting 6 with Premier pellets, did the 1:12″ barrel exceed the factory 1:16″ barrel.

If you look at the results of the 1:22″ barrel, you’ll note that it falls apart at 25 yards. It held its own at 10 meters; but at 25 yards, it falls far behind the factory barrel.

The 1:12″ barrel does the same, but it doesn’t open up as much as the 1:22″ barrel. There are individual instances where one of the two Quackenbush barrels exceeds the other; but in general, what I’m saying holds true. The factory barrel, however, doesn’t work that way.

The factory barrel holds together at 25 yards, just as it does at 10 meters. Again, there’s a single instance at 25 yards where it is beaten by the 1:12″ barrel (power setting 6 with Premier pellets), but that stands out as the only time the factory barrel was beaten at 25 yards. We can say in this test the factory 1:16″ twist barrel outperformed the other two barrels at 25 yards. That allows me to say two things.

First, I predict that the factory barrel will be the most accurate at 50 yards. Second, I believe that the 1:16″ twist rate is the best twist rate of the 3 we’ve tested.

Don’t get too excited
This test has been too small to say anything with certainty. I said that before we began, and I’m saying it again now. All these results can do is suggest things that should be looked at more closely. Other pellets will give different results — I’m sure of that. And more testing will refine these numbers. Where there’s gross separation between the Quackenbush barrels and the factory barrel, I feel certain the trend will continue with more testing. But where things are close, there might be a reversal of the outcome. There simply isn’t enough test data to say otherwise.

Conclusions so far
Based on the data we see thus far, I think that the 1:16″ twist rate seems to be the best of the three twist rates we’ve tested. At 10 meters, the factory barrel shot 3 of the best 6 results. At 25 yards the factory barrel shot 5 of 6 groups better than the other 2 barrels. Out of the total of 12 results, the factory barrel was the best 8 times. So, 67 percent of the best groups in this test were shot by the factory barrel.

The factory barrel is the best overall barrel in this test so far, and it gets better the farther the distance is to the target.

Because the other 2 barrels beat the factory barrel one-third of the time, I think the question of their quality can be laid to rest. Clearly, they’re giving the Lothar Walther factory barrel a run for the money.

Power versus accuracy
In Part 8, I talked about not needing to use power setting 10 with the 1:22″ barrel if it proved to be accurate enough. The velocity at power setting 6 was so high that I said I could stop there and conserve air. I think I’ve now shown that it isn’t accurate enough. Yes…when you look only at that barrel’s accuracy, you could surmise that it’s accurate enough at power setting 6 to stop at that point. But when the factory barrel is brought into the equation, the 1:22″ barrel falls behind.

What’s next?
Next, I’ll shoot all 3 barrels at 50 yards. I’m planning to shoot only power settings 6 and 10 with each barrel because of the distance involved. This will be outdoors, and the pellets will really scatter in the light breezes if they’re shot on the lowest setting. I will have to wait for ideal range conditions, so it may be quite a while before I’m able to make my next report.

How does rifling twist rate affect velocity and/or accuracy? Part 8

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

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

Today, I’m presenting the first part of the data collected thus far in this extensive test. My thanks to blog reader Fred DPRoNJ (Democratic People’s Republik of New Jersey) for creating the original spreadsheet for this data. Although I didn’t use his spreadsheet in the publication, I did use it as my worksheet to put this report together. Thanks, Fred!

This is a look at how the twist rate of rifling affects the velocity and accuracy of pellets in an AirForce Talon SS rifle in .22 caliber. We’re testing the same 2 pellets in each of 3 different barrels in the same gun. All 3 barrels are the same 12-inch length. Two of the barrels were custom-made by big bore airgun designer/maker Dennis Quackenbush for this test, and the other barrel is a factory Lothar Walther barrel that comes with the rifle. I chose this airgun for two reasons. First, it allows the quick barrel change that makes this test possible. Second, it has adjustable power so we can vary the power for each pellet we test.

I’m testing the rifle with 2 pellets. The first is the 14.3-grain Crosman Premier that has long been established as one of the most accurate pellets for a .22-caliber Talon SS. The second pellet is the 15.9-grain JSB Exact pellet that I’ve found will sometimes exceed the Premier for accuracy. I don’t believe there’s another pellet in the world that can match either pellet’s performance in my .22-caliber Talon SS.

Velocity first
Velocity was the first thing I tested, and it will be the only thing I report today. There’s too much data in this test to dump it all in a single report, so the accuracy portion of the test will follow tomorrow.

I shot 10 shots with each pellet at each of 3 different power settings on the gun — zero power (as low as the gun will go), power setting 6 and power setting 10. That was done in each of the 3 barrels, so there are a total of 18 outcomes to this test. Those 18 outcomes are shown in the table below.

My Talon SS doesn’t have a power setting scale etched on it, so I put a piece of tape on the side of the gun above the power window. Zero power is with the power-indicating Allen screw head all the way to the left in the window (the same as it would be on a gun that has an index etched on it). I put marks on the tape where power settings 6 and 10 are. I’ve tested many hundreds of these guns over the years that I know where the power screw head has to be, so these settings are quite accurate. The fact that I used the marks for each test (by centering the screw head on the mark) means that everything was identical for each test.

Talon SS power settings
The power settings were the same for every test.

Talon SS velocity table for rifling twist effect

General observations
First, I note that in all cases the velocity increased the most between power setting zero and setting 6. The velocity increase from setting 6 to setting 10 was always smaller than the increase from setting zero to setting 6, and that’s irrespective of the twist rate or which pellet was shot.

It’s true that there’s more variation between power setting zero and power setting 6 than between settings 6 and 10, but what you’re seeing here is the slowing down of the rate of velocity increase. That becomes clear in a moment when I discuss the rifle’s maximum velocity potential.

Next, I noted that, as the twist rate slowed (1:22″ is slower than 1:12″), the velocity increased at most power settings with most pellets. There was one instance with the 1:22″ barrel where the 15.9-grain JSB Exact pellet actually went 2 f.p.s. slower at setting 10 than at setting 6, but with all other barrels and all pellets, there was always a velocity increase as the power setting went higher.

Focusing on the 1:22″ barrel for a moment, we see that the velocity increases between setting 6 and setting 10 were not as great as they were in either the factory (1:16″) barrel or the 1:12″ barrel. This suggests what we have suspected all along — that the twist rate of the barrel does slow down the pellet as it gets tighter. And we can see from this test that the phenomenon is most apparent at the lower power settings. At the higher power settings, the differences seem to shrink, indicating that the influence of the power setting is overriding the influence of the twist rate. I believe this is an important finding, and it sets up the next observation, which is that the top velocity of the gun was fairly close for all 3 barrels, regardless of the twist rate. The type of pellet made more difference to the top velocity than the barrel twist rate did.

Specific things we learn from this test
It should be obvious from these results that the Talon SS powerplant has upper limits that cannot be exceeded by forcing more compressed air through the barrel. Better than anything I’ve seen, this illustrates the relationship between barrel length and velocity in a pneumatic airgun. Last week, I had an inquiry from a budding inventor who wanted to know the fastest pellet velocity I had ever witnessed. After I told him what it was, he told me he was working on an airgun design that used compressed gas at 5,000 to 6,000 psi, implying that this would increase the velocity. He told me that he had done extensive research on the internet and was unable to find anything on this topic, despite several of my own reports that address this very thing.

My point is that I get such inquiries all the time from people who are not yet connected to the airgun community and are out there reinventing the wheel. They’re working on a supposition that we all recognize as erroneous — namely that higher reservoir pressure gives higher velocity — but they haven’t gotten far enough into the subject to know that yet. This test serves as a foundation for why we say that barrel length affects velocity in a pneumatic gun.

A second thing that I found interesting is that power setting 6 is very close in performance to power setting 10. In the case of the 1:22″ twist barrel, it’s remarkably close…but it’s close for all three barrels. A prudent airgunner might consider this when setting the power wheel adjustment on his Talon SS, knowing that a lower setting uses less air, yet gives velocity that isn’t that much slower.

A third thing is that the velocity performance of the 1:22″ barrel is so good at power setting 6 that it makes power setting 10 useless. Take that thought just a little farther, and you’ll see that all power settings above setting 10 are pretty much a waste of air in a Talon SS with a 12-inch barrel, regardless of which pellet you use.

If the 1:22″ twist barrel turns out to be accurate, we’ll want to use it in the Talon SS instead of the factory 1:16″ barrel because we’re getting the same performance at power setting 6 that the factory barrel gets at setting 10. On the other hand, there’s not much real velocity difference between the 1:12″ barrel and the factory 1:16″ barrel. So, whichever one is more accurate is the one to go with if the 1:22″ barrel proves not to be as accurate.

That’s all I have to say, but I’m sure that some of our readers will have even more observations to add. Let the discussions begin.

How does rifling twist rate affect velocity and/or accuracy? Part 7

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

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6

This is Part 7 in this lengthy test series that looks at the effects of the rifling twist rate on both velocity and accuracy of a pellet rifle. Today, we’ll look at the 1:22 barrel, which means the pellet will turn once in each 22 inches of barrel it traverses. Of course, the Lothar Walther barrel in the .22-caliber AirForce Talon SS rifle I’m using is only 12 inches long, so the pellet doesn’t even turn one time before it leaves the muzzle, but that twist rate sets the pellet in rotational motion as it flies through the air to its target. The rotational speed will be less than what the 1:16 factory barrel imparts, and much less than the 1:12 barrel we have also tested.

Dennis Quackenbush made the two custom barrels I’m testing against the factory barrel with its 1:16 twist. So far, we’ve tested velocities with 2 different pellets at 3 different power settings for all three barrels (see Parts 2 and 3), and I did a short analysis of those tests in Part 4. Then, we tested the accuracy of the custom 1:12 barrel with both pellets at all 3 power settings at 10 meters, and again at 25 yards. Next, we did the same thing with the factory barrel.

Today, we’ll look at the accuracy of the 1:22 barrel with both pellets at all 3 power setting at 10 meters and again at 25 yards. In the next report, I’ll summarize the entire test to this point for you — comparing all 3 barrels for both power and accuracy. After that, I plan on testing all three barrels for accuracy at 50 yards. At that distance, the pellets will be spreading and accuracy benefits should show up vividly.

On to today’s test — the 1:22 twist-rate barrel.

Ten-meter testing

First up was the 14.3-grain Crosman Premier pellet. I had to remove and remount the scope, and the pellets were now striking to the left and low of the bullseye, but I left it there because where the pellets land doesn’t really matter in this test.

Ten pellets made a group that measures 0.258 inches between centers. Besides being tight, it’s a very round group, indicating the pellet likes this twist rate and power setting.

AirForce Talon SS rifle Premiers 10 meters zero power
Ten Premiers on zero power made this nice round group at 10 meters. It measures 0.258 inches between centers.

Next came 15.9-grain JSB Exact pellets on zero power. They also made a round group, but it was larger, at 0.324 inches. This is still a very nice group, but not as nice as the Premier group on the same power setting.

AirForce Talon SS rifle JSB Jumbo 10 meters zero power
Ten 15.9-grain JSB Exact Jumbos on zero power made this group at 10 meters. It measures 0.324 inches between centers.

Next, the power was dialed up to 6, and I shot a second group of Premiers. This time, the group was wider than it was high and measured 0.293 inches between centers. That’s smaller than the previous group of JSBs but slightly larger than the Premiers on the zero power setting.

AirForce Talon SS rifle Premiers 10 meters 6 power
Ten Premiers on power setting 6 made this group at 10 meters. It’s more horizontal than vertical and measures 0.293 inches between centers.

Following that, I shot 10 JSB Exacts on setting 6. They gave a group that is more vertical and measures 0.309 inches between centers.

AirForce Talon SS rifle JSB Jumbo 10 meters 6 power
Ten 15.9-grain JSB Exact Jumbos on power setting 6 made this group at 10 meters. It measures 0.309 inches between centers.

Easy loading
I noticed at this point in the test that both pellets were loading very easy into the breech. I wouldn’t call them loose — just very easy to load.

It was time to dial the power up to 10 and see what happened. Premiers went first, and 10 of them went into 0.288 inches. That’s just slightly larger than the first 10 on zero power.

AirForce Talon SS rifle Premiers 10 meters 10 power
Ten Premiers on power setting 10 made this group at 10 meters. It measures 0.288 inches between centers.

And, finally, I shot 10 JSB Exacts at 10 power. They spread out more than expected, giving a group measuring 0.53 inches at 10 meters. That was by far the largest 10-meter group.

AirForce Talon SS rifle JSB Jumbo 10 meters 10 power
Ten 15.9-grain JSB Exact Jumbos on power setting 10 made this group at 10 meters. It measures 0.309 inches between centers and is the largest 10-meter group made by the rifle.

What I see here is that Premiers are very stable in the 1:22 barrel. There is little difference in group size at any power setting. JSB Exacts, on the other hand, get progressively worse as the power increases. If we see this much dispersion at 10 meters the difference should be even more visible at 25 yards.

25-yard testing

First up at 25 yards was the Crosman Premier with the power set to zero. The 10-shot group landed very low on the target paper, and measured 0.671 inches between centers.

AirForce Talon SS rifle Premiers 25 yards zero power
Ten Premiers on power setting zero made this group at 25 yards. It’s very low on the paper and measures 0.671cinches between centers.

Next, I tried 10 JSB Exacts at the zero setting. They were horrible — making a vertical group measuring 1.949 inches between centers. I won’t shoot this pellet at this power at 50 yards because they would go off the paper!

AirForce Talon SS rifle JSB Jumbo 25 yards zero power
Ten 15.9-grain JSB Exact Jumbos on power setting zero made this 1.949-inch group at 10 meters. That’s all for this pellet at this power setting.

Next, the power was increased to 6 and Premiers were loaded again. Ten of them made a horizontal group that measures 0.845 inches between centers.

AirForce Talon SS rifle Premiers 25 yards 6 power
Ten Premiers on power setting 6 made this group at 25 yards. It’s horizontal and measures 0.845 inches between centers.

Then it was the JSB pellet’s turn. Ten Exact Jumbos landed in 1.797 inches, which is a little smaller than the group when the power was set to zero. If I try to extend this pellet and power setting out to 50 yards, I’m very likely to get a 7-10-inch group.

AirForce Talon SS rifle JSB Jumbo 25 yards 6 power
Ten 15.9-grain JSB Exact Jumbos on power setting 6 made this 1.797-inch group at 10 meters.

Finally it was time to try the pellets on power setting 10. Here they would be traveling their fastest, which means the spin rate would also be highest for this barrel. According to the theory, the groups should get smaller.

Premiers went first, and 10 of them landed in a group measuring 1.082 inches between centers. That’s larger than both groups that went before. Since the velocity increased, the Premiers spread out. Interesting!

AirForce Talon SS rifle Premiers 25 yards 10 power
Ten Premiers on power setting 10 made this group at 25 yards. It’s horizontal and measures 1.082 inches between centers.

Finally, it was time to try the JSB Exact Jumbos on power setting 10. This time the theory did play out as expected, because 10 pellets made a group measuring 1.172 inches between centers. It’s smaller than the group from both of the lower power settings, and those groups decreased in size as the power increased.

AirForce Talon SS rifle JSB Jumbo 25 yards 10 power
Ten 15.9-grain JSB Exact Jumbos on power setting 10 made this 1.172-inch group at 10 meters.

Conclusions
Premiers behaved differently than JSB Exact Jumbos in this test. They did not become more accurate as the velocity increased, and I think I can suggest a reason why. JSBs are longer than Premiers. Premiers measure 0.269 inches in length, while JSB Exact Jumbos measure 0.296 inches in length. At their widest, which is the skirt, Premiers are 0.220 inches in diameter, while JSBs are 0.222 inches across. So, JSBs are longer than Premiers, in relation to their diameter, and that makes them harder to stabilize.

AirForce Talon SS rifle 2 pellets
The JSB Exact Jumbo on the left is longer than the Crosman Premier on the right. That makes it harder to stabilize and it needs to spin faster.

That was one of the problems I had with the .22 Hornet centerfire rifle I reported on last week. It shoots its bullets very slow, relative to other .22 centerfires, yet the twist rate is 1:16, where other .22 centerfires are 1:12, or in the very specialized instance of the .223/5.56mm, anywhere from 1:7 to 1:12. That’s why I’ve been writing about these rifles — so we can all gain an appreciation for how twist rates affect accuracy. The .22 Hornet can only do its best with short, fat bullets of relatively light weight. Now, you see the same thing in a pellet rifle.

Today, we see a very dramatic result of how the twist rate affects accuracy. We learned in our test of the smoothbore pellet gun that while a gun may be accurate at 10 meters, it may fall apart at 25 yards. Today, we see that in a rifle that has a very slow twist rate doing the same. If we wanted to use this twist rate, we would need to shoot only very short pellets so they could stabilize. See how it works?

Next, I’ll write up a summary article of the test to this point so we can get a grip on all the data that’s been generated. Of course, it’s all here for you now. All you have to do is go back and look at the results of all the testing to see how the twist rate affects both velocity and accuracy.

Following the summary report, I’ll test all three barrels at 50 yards.

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