Airgun Barrel Twist Rate – Does It Matter?

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Now I have not shot firearms in many years. However, I remember that barrel twist rate always seemed to be a big deal in the powder-burning world.

Recently I was reminded of that when browsing the Midway USA website. Take a look at the product description pages for just about any firearm and there – among the key product specifications – is barrel twist rate.

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Looking further, I find much Internet information and discussion about twist rates, particularly for AR 15-type “black rifles”.

What interests me about this is that relatively small differences in twist rate – say 1 in 7 or 1 in 9 (Inches) are attributed with considerably different levels of accuracy downrange, depending on the bullet weight.

Moreover, the results of these differences in twist rate seem to be significant even though the bullet weights and basic shapes of the projectiles look RELATIVELY similar – at least to me.

Now it’s important to understand that I am MOST DEFINITELY NOT A BALLISTICIAN. (My above comments undoubtedly prove that statement to be true!)

However, my understanding is that – at least in the powder-burning world – longer and/or heavier bullets benefit from a faster twist rate. That led me to start thinking about airguns…


What Is Barrel Twist Rate?​


Rifled barrel have a series of “lands and grooves” cut into the bore. We looked at them recently in this Hard Air Magazine post.

What's Inside Your Airgun Barrel? First Borescope Results


In fact, these lands and grooves are not parallel to the direction of the bore, they are cut in a slow spiral. In other words, they are “twisted”.

Thus the twist rate is the length along the barrel taken for the bullet, pellet or slug to make one 360 degree rotation as it passes down the barrel. It’s expressed in Inches: for example a “16-Inch twist rate” tells that there’s one rotation for every 16 Inches traveled down the barrel. It’s usually written 1:16.


Does Airgun Barrel Twist Rate Matter?​


Generally, I find very little discussion of airgun barrel twist rates. It’s often not easy at all to find out the twist rate for the barrel of the air rifle you’re planning to buy, or even of the one you have.

Yet this is starting to change, a little!

Airgun Barrel Twist Rate


The appearance of slugs has raised interest in airgun barrel twist rates, with them being different for “slug barrels”, for example.

At the 2024 IWA OutdoorClassics show recently, twist rates were quoted for some air rifles. This was particularly marked in the case of Eastern European brands, I noticed.

Still, I am surprised that there is not more interest in this topic among airgunners. After all, the range of profiles and weights for airgun ammo has increased dramatically in recent years and continues to do so.


Airgun Ammo Variability​


Compared to firearms, airgun ammo has some vary major differences. There’s the huge difference between waisted, “Diabolo” pellets and parallel-sided slugs, for example. Then there’s major differences between head profiles – from flat-fronted wadcutters through domes to pointed pellets, hollow points and everything in between.

Plus, the weight differences are extreme, too.

To focus our discussion a little, let’s concentrate on .22 caliber for two reasons. There’s a huge variety of ammo available, plus we can make a few comparisons to .22 firearm calibers also.

The “traditional” average weight from .22 caliber lead pellets has been in the 14 – 15 Grain range. Think 14.3 Grain Crosman Premiers, for example. However, the lightest .22 caliber lead-free pellets (Predator GTOs) come-in at just 11.75 Grains.

Airgun Barrel Twist Rate


Now to the other extreme. The heaviest .22 caliber lead pellet I am aware of is the 33.96 Grain JSB Jumbo Beast.

Moving to slugs, the heaviest normal production slugs I know weigh 40 Grains. These are the H&N Slug HP heavies, although others have matched that weight, too.

Making a very simple comparison between ammo weights, we see:

Min Projectile WeightMax Projectile WeightRatio Min To Max
.22 Cal Airguns11.75 Grains40 Grains3.4 X
.22 LR Firearms20 Grains60 Grains3.0 X
.223 Cal Firearms35 Grains112 Grains3.2 X

As we see, .22 caliber airgun ammo is at least as variable in weight as .22 LR and .223 caliber powder-burning ammo. PLUS, there’s the huge differences in shape, too, that’s not present in firearms bullets to anything like the same extent.

Yes, I know there’s significant velocity differences between the three types, but I’m putting that on one side for this discussion.

Anyhow, I would have thought that – as barrel twist rate is a significant issue for .22 LR and .223 firearms, they ought to be for .22 caliber airguns as well. And – by extension – for other airgun calibers also.

We’ll explore this topic further in another HAM post…


The post Airgun Barrel Twist Rate – Does It Matter? appeared first on Hard Air Magazine.
 
Love em or hate em FX has been huge in pushing slugs to the front of many airgunners minds. I know the lighter slugs (say 21/23 gr) are supposed to work well in their 'regular pellet' barrels. The heavy slug barrels are needed for accurate results on the bigger slugs. My S510 shoots the lighter stuff decently as well but not enough to replace a good ol 18gr Jsb! My Ghost HP is laughable with slugs. It has been said it has a 1:30 twist rate, so makes sense. Shot a few out of it....one went left, one went high, one went low, I gave up at that point😅 I find even the manufacturers themselves rarely point out the twist rate of their air guns. Either they like to keep it hush hush, or they figure if the gun is accurate, the new owner doesn't care?! They mention speed, weight, etc but rarely twist rate. I don't care enough to know (apparently 🤣) what my TX, Slavia, or S510 twist rate is.
I don't know man. But what I do know is when I put that TJ barrel on my FX Impact X mk2 .357, slugs and pellets are sub moa or moa at 100 yards shooting 79, 93 NSAs Zans, FXs Griffins at 960 to 970. I couldn't make that happen with them darn STX or Superior liners. It just was not happening for me. I know you gotta find what slug or pellets works best but, come on! People spend 17 to 2700.00 on FX guns so you'd think the barrel wouldn't be an issue at all, but it is.
 
I recently posted in another forum here on the Community about twist rates.

I shoot exclusively .25 caliber, and for the most part, NSA 26.8 gr. slugs. The fastest twist rate that FX sells for .25 caliber is 1:18. All of the various calculators all say this is close to the correct twist. I feel it is not!

I live in an area which hovers around 3,500 FoS, and the daytime temperatures hover around 90°+ in the Summer. Yet, in order to stabilize these tiny slugs, velocities have to be above 990 FPS, or key holing occurs. I could prove this easy enough, but FX apparently is unable (or unwilling) to produce say 1:16 or 1:14 barrels.
 
I recently posted in another forum here on the Community about twist rates.

I shoot exclusively .25 caliber, and for the most part, NSA 26.8 gr. slugs. The fastest twist rate that FX sells for .25 caliber is 1:18. All of the various calculators all say this is close to the correct twist. I feel it is not!

I live in an area which hovers around 3,500 FoS, and the daytime temperatures hover around 90°+ in the Summer. Yet, in order to stabilize these tiny slugs, velocities have to be above 990 FPS, or key holing occurs. I could prove this easy enough, but FX apparently is unable (or unwilling) to produce say 1:16 or 1:14 barrels.
neither does lothar walther
 
I recently posted in another forum here on the Community about twist rates.

I shoot exclusively .25 caliber, and for the most part, NSA 26.8 gr. slugs. The fastest twist rate that FX sells for .25 caliber is 1:18. All of the various calculators all say this is close to the correct twist. I feel it is not!

I live in an area which hovers around 3,500 FoS, and the daytime temperatures hover around 90°+ in the Summer. Yet, in order to stabilize these tiny slugs, velocities have to be above 990 FPS, or key holing occurs. I could prove this easy enough, but FX apparently is unable (or unwilling) to produce say 1:16 or 1:14 barrels.
This might sound silly, but have you tried a slower twist rate at a lower speed?
 
Yes I have. The 'pellet' barrel is 1:24, and it will not stabilize the 26.8 gr slugs, except in rather cold weather.

The present velocity is 1,011 ± 2, which is excellent consistency. Any less, and fliers start occurring on a regular basis.
 
I don't know man. But what I do know is when I put that TJ barrel on my FX Impact X mk2 .357, slugs and pellets are sub moa or moa at 100 yards shooting 79, 93 NSAs Zans, FXs Griffins at 960 to 970. I couldn't make that happen with them darn STX or Superior liners. It just was not happening for me. I know you gotta find what slug or pellets works best but, come on! People spend 17 to 2700.00 on FX guns so you'd think the barrel wouldn't be an issue at all, but it is.
Wow that is alotta FPE! Agreed, I mostly mean people see the FX guys shooting FX guns with FX slugs and go down the same rabbit hole hoping to shoot slugs well. But often more $$/parts are req to get em shooting sweet, and poi from any abuse is real. In no way shape or form do I think they do it best, just that they pushed it hardest on YT and other platforms. Their barrel systems turned me away, went BRK will be holding out till they offer a slug barrel for my Ghost.
 
Well, for me it took some research then some un-brain washing. There was a guy on YT that helped me to see the barrel quality importance. It really makes a huge difference.
 
Take a look at these numbers.
 

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Yes I have. The 'pellet' barrel is 1:24, and it will not stabilize the 26.8 gr slugs, except in rather cold weather.

The present velocity is 1,011 ± 2, which is excellent consistency. Any less, and fliers start occurring on a regular basis.
Use this my boy and you'll never have that problem again.
 

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This is from an article I was reading. "Stability is related to spin rate (or RPM), and how RPM, is determined by barrel twist rate and velocity. A bullet that is fired with inadequate spin will have a Gyroscopic stability factor, SG less than 1.0 and will tumble out of the barrel. If you spin the bullet fast enough to achieve an SG of 1.5 or higher, it will fly point forward with accuracy and minimal drag." There are many twist rate stability calculators on-line that will determine the SG of your setup. The higher the SG number the better and the longer range you will get accurately. Remember it is spin RPM so the faster you can push it the better.

 
The problem with just about all of the stability calculators, including Bob McCoy's McGyro program, is that they are much simplified systems, which assume a solid shot and use aerodynamic approximations which become inaccurate at certain speeds. Hollow point slugs, many with hollow bases, are anything but solid, so the stability programs will calculate inaccurate values for their centre of gravity and moments of inertia.

Unfortunately, there is no easy way round calculating the required twist rate that I know of, particularly at speeds approaching Mach 1 (1116.5 ft/sec) where even the best simple programs can be way out. You need to know the centre of gravity position of your slugs and the moments of inertia if you want reasonable estimates. More accurate aerodynamic moment estimates would also help, particularly at the speeds mentioned above. Only more complex programs can give you those estimates.

I am surprised that the program shown says that an Sg greater than 6 is in the ideal range, since it is way more than the normally accepted figure of 1.5 for maximum BC. I would anticipate a loss of accuracy at long ranges, where the Sg may increase to unacceptably high values.
 

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