Does anyone know what the twist rate of the FX smooth twist barrels are, specificly the Bobcat MkII .25
Twist rate of FX smooth twist barrels
- Thread starter Doug
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I believe 1:16 but could be way off. If memory serves correct, most popular .25 bores are 1:15-1:18 twist. Though not a factory used barrel, the TJ .25's are 1:14 and 1:22. I did a couple searches and If I read the old posts correctly, Harry(yrrah) said 1:16 and I believe Dave G also said 1:16. These were old posts from another forum, but hope that helps.
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Fredrik told me the .22 ST barrels were 1:16" to that point in time a couple of years ago. I don't know if the Bobcats are/were any different.
However the question you didn't ask was what the pellet spin rate is when it emerges from that couple of inches of "rifling" after stripping through the "rifling".
Fredrik and FX have processed many iterations of the ST barrels.
Dan Brown measured spin rate at 1:160", (that is not a typo error) , early on..
I measured my .22 cal at 1:64" ; and a .25 cal at approx 1:75" from later barrels. But it also depended upon pellet weight and velocity as reflected in the momentum of the pellet when it impacted the couple of inches of "rifling" at the muzzle..
Fredrik then measured a .22 cal as 1:44" spin rate from memory. That was from an 18th iteration barrel ( mine was a 16th).
Some two years ago after Fredrik and I had discussions about this (it had been news to him then) Fredrik was thinking of producing some for us to test in 1:30" to 1:40 "rifling" twist . However his ST barrels were shooting as well as any other barrels, for their purposes, and as the machines that produce them are complex and expensive, I don't know, but don't think, he experimented further with the idea of trying to match the spin rate -to-rifling rate such that stripping of the pellet did not happen. I could conjecture that such a change may have just as likely been detrimental to the proven accuracy of the system.
But back to your actual question; 1:16" was the standard ST rifling rate. .... Harry.
However the question you didn't ask was what the pellet spin rate is when it emerges from that couple of inches of "rifling" after stripping through the "rifling".
Fredrik and FX have processed many iterations of the ST barrels.
Dan Brown measured spin rate at 1:160", (that is not a typo error) , early on..
I measured my .22 cal at 1:64" ; and a .25 cal at approx 1:75" from later barrels. But it also depended upon pellet weight and velocity as reflected in the momentum of the pellet when it impacted the couple of inches of "rifling" at the muzzle..
Fredrik then measured a .22 cal as 1:44" spin rate from memory. That was from an 18th iteration barrel ( mine was a 16th).
Some two years ago after Fredrik and I had discussions about this (it had been news to him then) Fredrik was thinking of producing some for us to test in 1:30" to 1:40 "rifling" twist . However his ST barrels were shooting as well as any other barrels, for their purposes, and as the machines that produce them are complex and expensive, I don't know, but don't think, he experimented further with the idea of trying to match the spin rate -to-rifling rate such that stripping of the pellet did not happen. I could conjecture that such a change may have just as likely been detrimental to the proven accuracy of the system.
But back to your actual question; 1:16" was the standard ST rifling rate. .... Harry.
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Guys, thanks for your info. I read somewhere in the recent past, can't recall exactly where or what the posting date was, but someone had stated that the .22 cal ST barrel had a twist rate of 1:159", that's 13 feet. My thoughts were wow... really...????? That's what prompted my question and Harry confirmed it.
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