GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: oldpro on November 21, 2015, 03:15:11 AM
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Has anyone produced a variable twist rifle barrel in any rifle market?
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Has anyone produced a variable twist rifle barrel in any rifle market?
Not sure if you mean progressive twist but that has been done.
http://www.bartleinbarrels.com/Trifling.htm (http://www.bartleinbarrels.com/Trifling.htm)
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S&W 460. Gain twist. Can't imagine needing one in an air rifle.
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Not seeing any advantage...and a few disadvantages.
I would rather see a boolit shooting barrel with shallower lands. Make sure the bore will fit the selection of boolits you'll run; nose riders I particular will be sensitive to this. No sense wasting the potential ME on cutting/swaging deeper grooves than is needed.
cheers,
Douglas
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A progressive twist will result in some degree of smearing of the grooves engraved in the bullet, because the angle of the land must change as the bullet moves down the barrel.... That displaced lead has to go somewhere.... and results in the grooves in the bullet being wider than they would with a constant twist.... The amount of energy used to spin up a bullet is VERY small.... The difference between a 14" twist and a 7" twist in a .257 cal is about 1.2 FPE at 1000 fps.... If you end up at that 7" twist, it doesn't make a difference in the energy how you get there.... All that changes with a progressive twist is that the stress on the bullet is less when it first launches (when the acceleration is the greatest).... but less energy absorbed initially means more later in the barrel.... The FX Smooth Twist barrels, which only have rifling at the muzzle, strip the outside of the pellet completely, recovered pellets show basically no rifling marks, and are only spinning very slowly compared to the twist of the rifling.... but that is a different situation than a true progressive twist....
Bob
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I wonder about a Benchmark 2 groove for lead bullets, they are a great.22lr match barrel.
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I wonder about a Benchmark 2 groove for lead bullets, they are a great.22lr match barrel.
Boolits for the .22 lr bore are different from the center fire .224-5 stuff. If I could get LR projectiles inexpensively than absolutely worth doing...:) An Anschutz SuperMatch barrel is 690 mm long...:)
cheers,
Douglas