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 Post subject: Barrel twists
PostPosted: Sun Nov 10, 2019 1:10 am 
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Joined: Mon May 06, 2019 4:07 pm
Posts: 93
So obvously matching the correct pellet to your barrel twists dramaticaly increases accuracy. How do you figure out your barrels twist rate?


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 Post subject: Re: Barrel twists
PostPosted: Sun Nov 10, 2019 7:30 am 
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Joined: Mon Aug 08, 2016 7:23 am
Posts: 2782
Location: Somewheres near the Atlantic
If I remember but been awhile. But you need a cleaning rod, a patch on it, measuring tape and a piece of tape.

Premise is the patch digs into the rifling and turns the rod. The tape acts as a flag so you can see the rotations.

Larry explains it simple.

https://www.youtube.com/watch?v=cdoCNZBlRGQ


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 Post subject: Re: Barrel twists
PostPosted: Sun Nov 10, 2019 1:04 pm 
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Joined: Wed Jan 05, 2011 12:35 pm
Posts: 6019
Location: P.G. B.C.
Measuring the rate of twist is easy, however, you still have to try different pellets to see what shoots best.
There is no known literature that tells you what pellet to use with ? rate of twist, thus, back to the drawing
board on testing different pellets.
It's pretty much a crap shoot - you have to do the shooting to find what your rifle or pistol likes.
Knowing the rate of twist is in no way, a help. It is what it is. This is not like matching bullet weights/lengths
for a Centre Fire rifle.
Some guns like heavy for calibre pellets, some don't. Some like Crossman Pellets, some don't.
MOST like the typical-for-calibre JSB pellets, meaning 8.2/4gr. in .177 and 14.2/4gr. in .22. Some prefer H&H's, like my .22's.

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Daryl


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 Post subject: Re: Barrel twists
PostPosted: Sun Nov 10, 2019 1:22 pm 
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Joined: Mon May 06, 2019 4:07 pm
Posts: 93
Ok seen lots of videos were people say you should try to find the best pellet for your twist rate by pushing a pellet down the barrel and measure the diamater of the pellet with the barrel forget the exact process


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 Post subject: Re: Barrel twists
PostPosted: Sun Nov 10, 2019 4:33 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8979
Location: Coalmont BC
Twist rates for pellets are currently undergoing a HUGE change.... Diabolo (waisted) pellets are drag stabilized, like a Badminton shuttlecock, and need very little spin.... Most airgun manufacturers have not yet even started to change over to the new, slow twist barrels.... Sean Pero and I started the trend with the 26" twist .30 cal. barrel we designed for TJ's, which won the EBR in 2014.... Some, like FX, are starting to produce slower twist pellet barrels, with their new STX series liners.... Here is a chart of what they are currently producing....

Image

Note they are now using a 27" twist in .25 cal and a 40" twist in .30 cal.... These are similar to the 18" twist of the .177 cal.... The only caliber where they don't have a twist rate that is 100 calibers long, or slower, is in .22 cal. where the slowest twist is 19".... That surprises me, I think you will see a slower twist .22 cal pellet liner from them in the near future.... something on the order of 22".... American Air Arms, in their EVOL series, which are designed for pellets, not slugs, are using a 32" twist in .25 cal and a 42" twist in .30 cal, even slower than FX.... :shock:

Slugs are an entirely different matter.... You need to spin them fast enough to get gyroscopic stability....

Bob

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Proud Member of the 2000+fps Club!


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 Post subject: Re: Barrel twists
PostPosted: Sun Nov 10, 2019 8:03 pm 
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Joined: Mon May 06, 2019 4:07 pm
Posts: 93
Ok intresting because like 90% of air guns have rifling wich is a twisted grove for the pellet to follow. So i guess its more how snug the pellet is in the barrel to maintain stability in flight. Does anyone know how "snug" the pellet should be as it passes thru the barrel?


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 Post subject: Re: Barrel twists
PostPosted: Sun Nov 10, 2019 8:17 pm 
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Location: Coalmont BC
When you figure that out, let us know.... You can have two rifles of the same model that prefer different pellets, or sizes of pellets.... The rule regarding what pellet will work best in a given rifling twist is that there are no rules.... :roll:

Try it and see what your gun likes.... :wink:

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Re: Barrel twists
PostPosted: Sun Nov 10, 2019 10:26 pm 
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Joined: Mon May 06, 2019 4:07 pm
Posts: 93
Pretty sure thats because they each have a diffrent barrel twist (rifiling twist) and matching the pellet with the rifle twist gives you supreme accuracy just wondering how do you match them


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 Post subject: Re: Barrel twists
PostPosted: Mon Nov 11, 2019 8:41 am 
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Joined: Fri Aug 24, 2007 9:21 pm
Posts: 2127
Location: Greater Napanee, ON, Canada
Pretty sure Bob was inferring, same gun, same barrel, same twist, .... Two identical guns when you look at them will choose different pellets. I have three TX200s with identical barrels, tuned to the same power and each one shoots a different pellet. How do I know that? As Daryl and Bob suggested, I tried all the pellets and the gun chose their favourite one. One shoots JSB 8.44 in 4.53 head size, another shoots AA 7.87 in 4.52 head size and the last one shoots JSB 10.3 in 4.52 head size. The one shooting the heavies was a little bit of a surprise, as I usually do not even use them to test in the TX200, but a friend suggested to give them a try. Can't argue with pellets landing real close together at 50 yards and on a breezy day no less.

Long story short, I do as Daryl and Bob suggest and shoot until the gun choses a pellet. Heck, I love shooting anyway, so no hardship there. :D

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 Post subject: Re: Barrel twists
PostPosted: Mon Nov 11, 2019 9:09 am 
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Joined: Mon Aug 08, 2016 7:23 am
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Location: Somewheres near the Atlantic
Ravenairgun wrote:
Pretty sure thats because they each have a diffrent barrel twist (rifiling twist) and matching the pellet with the rifle twist gives you supreme accuracy just wondering how do you match them


Bob knows a thing or two about airguns. But you can have same gun, same barrel, but made on different machines, and give a different results. You can have 2 barrels made at a different time, on same machine and have different results, due to tooling wearing down, or different stock.

Only real positive method is just picking up pellets and finding out what shoots the most. Like a bunch others said. Also everybody shoots slightly different. So I can have the same pellets, barrel, gun as Bob and Ill get a different results.

Personally I never really heard much about matching pellets to rifle twist. In fact this post is the first one.


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 Post subject: Re: Barrel twists
PostPosted: Mon Nov 11, 2019 10:45 am 
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Joined: Fri Aug 24, 2007 9:21 pm
Posts: 2127
Location: Greater Napanee, ON, Canada
Same gun, same barrel, cut from same barrel blank one after the other, rifling cut on the same machine, with the same tooling, back to back and still they very well could choose different pellets. There are so many variables that predicting is a waste of time. Shoot!

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 Post subject: Re: Barrel twists
PostPosted: Mon Nov 11, 2019 11:20 am 
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Joined: Mon May 06, 2019 4:07 pm
Posts: 93
Lol may not be a waste of time if i can figure out what you are supposed to match with the barrel twist because im pretty sure its the mm of the pellet and the only thing i see change in the same caliber is the weight or shape of the head of the pellet maybe some one knows what you are supposed to match from the pellet to the barrel twist?


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 Post subject: Re: Barrel twists
PostPosted: Mon Nov 11, 2019 12:17 pm 
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Joined: Wed Jan 05, 2011 12:35 pm
Posts: 6019
Location: P.G. B.C.
Ravenairgun - you are not listening because you already have an idea in your head that is blocking the truth about the whole 'deal'.
I have a model 97 HW that loves, absolutely loves Cometa 4.51mm JSB's but will not shoot the standard JSB Diabolo 4.51's that LOOK
identical and are the same size & weight, exactly. The standard pellets shoot double the groups sizes, at 25 yards & do it consistently.
You have to shoot the gun. No amount of decifering/figuring/manifpulating of numbers is going to answer the problem of knowing which
pellet will shoot.

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Daryl


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 Post subject: Re: Barrel twists
PostPosted: Mon Nov 11, 2019 12:39 pm 
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Joined: Mon May 06, 2019 4:07 pm
Posts: 93
Ya no inunderstand what you guys are saying i mean there got to be some kind of diffrenece or somtjing that makes them fly diffrent is all im trying to say because if they were 100% identical they would fly the same....


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 Post subject: Re: Barrel twists
PostPosted: Mon Nov 11, 2019 1:14 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8979
Location: Coalmont BC
Pellets are different.... Barrels are different.... Put the pellet in the gun and see how it shoots, because no amount of measuring or calculating will tell you that.... :roll:

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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