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10 comments

Date Votes
  • 1fisher
    It is usually called gain twist rifling. It starts out with a slow twist at the chamber and increases the twist rate towards the muzzle.


    Some custom barrel makers use gain twist for target guns, but I think that the Carcano's were pretty much the only military or mass production guns with it.
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  • beantownshootah
    Fisher has it.

    "Gain twist" rifling just means the rate of twist increases as you get further down the barrel towards the muzzle.

    This feature is common in artillery pieces, and it used to be used in black powder revolvers, amongst others.

    In a more contemporary application, Smith and Wesson currently uses it in its recent-design large .460 X-frame revolver.

    The idea, in general, is to work the bullet slowly up to maximum spin/stability speed, rather than bang it up to max rotation instantly.

    It could be helpful for fragile bullets. Whether or not it helps accuracy it debatable.

    Smith is using this feature in its .460 revolvers to help reduce ROTATIONAL recoil. IE, when you have a really heavy .45 caliber slug hitting rifling really hard, it will cause the ENTIRE GUN to rotate in the opposite direction of the rifling. Having the bullet slowly spin up to speed is supposed to mitigate this a bit.
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  • XXCross
    The Germans used it on some of their heave artillery. Very little was gained and the hassle wasn't worth the effort.
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  • 7.62x39Lover
    Thanks guys. Very interesting.
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  • givette
    I don't like the concept. The bullet is constantly being 'swaged' into new rifling. Joe
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  • Alan Rushing
    givette, I'd concurr with your notions on the swaggggging! [;)]
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  • Hawk Carse
    I figure the Italians wanted to start the bullet off with minimum resistance in front of 1891 smokeless powder.

    Some old guy name of Harry Pope thought gain twist would help accuracy.

    There are some high end barrels being made now with a very slight gain, like half an inch of gain from breech to muzzle.
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  • RCrosby
    Read once that (some?) Pythons were made with gain twist.
    Yes?
    Thanks, Hawk, that was it. Memory ain't what it used to was![:D][:D]
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  • Hawk Carse
    No.
    They do have a bit of taper to the bore. Kind of like that Pope fellow did.
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  • v35
    Colt used it in their percussion revolvers to prevent stripping the engraving in round balls as little lead is in contact with the rifling.
    The same reasoning may apply to heavy artillery rounds having narrow copper or bronze rotating bands.
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