Armory Sponsor
Posted: 1/31/2010 2:41:05 AM EDT
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Does anyone know of a gun with variable twist? I was thinking a progressive twist might result in higher rotational velocity (more stability?) with less friction against forward motion... Maybe start out at 1:12 and end with 1:7 or something...
Any thoughts? Or do I need to quit surfing ARFCOM and get some sleep? 
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They're out there. I've only heard of them on bolt guns though. Looks like http://www.bartleinbarrels.com/Trifling.htm <–– they can do it on any barrel blank. |
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I've thought about it before, but I came to the conclusion that standard twist are just as effective. You need to figure that going to a faster twist is actually an acceleration, the bullet starts out at 0 degrees rotation per inch, hits the first and is rapidly accelerated, then the acceleration slow, is still accelerating the bullet at rate that will probably continue to accelerate to some degree after it exits the barrel. So your barrel may end at 1:7 but the bullet has the potential to reach a faster rotation. Then if you think of vectors, your pushing the bullet out the barrel and giving it a constant spin. With the progressive, your using more of your force to accelerate the bullet around the long axis and reducing the acceleration forward.
I'm not very well versed in physics, but this is my opinion on it. |
| The S&W 460XVR uses a gain twist barrel. Linky I have and older magazine that reviewed a 9" AR barrel that used polygonal gain twist. I'll see if I can dig it out and find anything online later. |
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Quoted:
I've thought about it before, but I came to the conclusion that standard twist are just as effective. You need to figure that going to a faster twist is actually an acceleration, the bullet starts out at 0 degrees rotation per inch, hits the first and is rapidly accelerated, then the acceleration slow, is still accelerating the bullet at rate that will probably continue to accelerate to some degree after it exits the barrel. So your barrel may end at 1:7 but the bullet has the potential to reach a faster rotation. Then if you think of vectors, your pushing the bullet out the barrel and giving it a constant spin. With the progressive, your using more of your force to accelerate the bullet around the long axis and reducing the acceleration forward. I'm not very well versed in physics, but this is my opinion on it. F=ma. You can't have continued rotational acceleration once the bullet exits the barrel- there is no force being applied (a la lands and grooves). I am neglecting air resistance. |
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