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Twist Rates in Air Rifles

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Pellets are designed originally to shoot out of smooth bore so they need very little twist rate/spin to stabilize it be accurate. But we are shooting them faster and faster and then have pellets that are heavier and longer like JSB redesign which needed a little more twists to stabilize. If you look at FX their pellet gun made a name for themselves for a barrel that has rifling only at the end. Most pellets guns have around 1:16 for 177, 1:18 for 22, 1:22 for 25 and almost 1:30 for 30. Mainly because as pellets get larger they get shorter(shorter projectile need less spin) and skirt get bigger and less spin is needed. 


when shooting a pellet from a slug barrel with too much twist the pellet if has poor balance will spiral out of control or you will get more fliers as pellets are harder to make 100% balanced. One way to “solve” that is to shoot slower or a lot slower. 



 
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Think of your standard pellet as one of those badminton birdy things. When you hit it, it takes a few feet and then it stabilizes itself and starts flying straight. That's exactly what a diabolo pellet does! They technically dont need any spin, like qball said.. but we put a spin on them to get them straight in a shorter amount of time which improves accuracy. The diabolo pellet hasnt changed any in several decades, but better rifling and barrels improved the accuracy. 

Slugs are the opposite, they need spin to stabilize them the whole way and often lots of it! So slug barrels are often faster twist rate, which pellets dont typically mind. You'll find the heavier pellets like more spin, and the lighter pellets like less. I know guys do good with the really heavy 25 cal pellets in slug barrels. 

Twist rate depends on the manufacturer. I think LW barrels are available in several twist rates last I looked. 



Wobbly or spiraling pellets are damaged pellets, caused by dirty grooves that cut an uneven pattern on the pellet or too tight of a barrel that damaged the head. They are thrown off balance aerodynamically and are spiraling as they try and straighten out. 
 
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I probably should go ask Bob....
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Yes, you should.

Over at www.GatewayToAirguns.org there are plenty of discussions and instructionals on both interior and exterior ballistics.

We just had one last week again.

❌Bob Sterne (rsterne) is as helpful as he is extremely knowledgeable. 

❌And Miles Morris is a professional ballistician....



Yes, lots of ballistic cool-aid, click bait, and what have you...!! 😄



Matthias


 
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Most pellets have between 1/20 to 1/30 twist, slugs generally like 1/10 - 1/16 twist. Pellets run good in almost all liners but in the fast twist liners if you shoot in the wind you will usually get a stability issue. But In dead calm wind you will shoot lasers. 



now the hybrid slugs can use a lesser amount of twist because there designed like a pellet. They have a hollow skirt which allows them to balance out quicker after leaving the barrel. 
 
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JungleShooter, that link doesn't work for me. In which sub-forum is the discussion at GTA?
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You're right, my mistake (I fixed it now).

🔶Here is "Bob and Lloyd's" sub-forum at GTA — lots of profound topics, and Miles Morris is right there, too:

https://www.gatewaytoairguns.org/GTA/index.php?board=224.0



🔶Bob finally collected a lot of his research and experience in a series of articles that he published with HardAir Magazine, here:

https://hardairmagazine.com/ham-columns/the-definitive-index-to-bob-sternes-ham-technical-articles/

We need to bug Bob to publish these in bookform — they would be great Christmas gifts!



🔶 Here's a definitive article and forum interchange by ballistician Miles Morris: "External Ballistics of Pellets"

https://www.gatewaytoairguns.org/GTA/index.php?topic=169459.0





⭐ I really appreciate how these guys are sharing their knowledge and experience with everyone else freely.

And there are many others like them, here at AGN, over at GTA, and at AGG and AGW — even competition shooters who could be excused for not wanting to share their secrets. But many do. ➔ I LIKE this community!! 😊 [Where is that LIKE button when you need it?!]



Matthias
 
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I know next to nothing about this topic, and that' an understatement

However here is a link to Lothar Walther air rifle barrels,that may add some info to the discussion

https://www.lothar-walther.com/gun-barrel-blanks/airgun-barrels/?p=1



I would like to ask

What is a polygon barrel?



Ed

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https://alchetron.com/Polygonal-rifling

https://youtu.be/2O84B700Li4

https://www.airgunnation.com/topic/polygonal-barrell-vrs-reg-lothar-barrel/

https://airgunaccuracy.wordpress.com/polygonal-and-rifled-barrels-compared-for-bc-and-velocity/




 
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