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Thread: Barrel rifling

  1. #1
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    Default Barrel rifling

    This is just a question out of curiosity.

    Take a barrel 22 cal, how many grooves should there be a 75mm barrel and how much angular twist, ie, quarter of a turn, more or less?

    How deep should the grooves be?

    Ken

  2. #2
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    This might help, RIFLE BARREL TWIST RATES

    Not sure on groove depths.

  3. #3
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    Ken ,
    This C & P comes from one of my rifle sites so I can't vouch that is 100% accurate but would tend to trust it as the .22 s I have owned/ used ,appear to by fairly shallow.

    .22 - 0.218"/0.219" - 0.224" - 0.0025"/0.003".

    I suspect there's no standard or hard and fast rule about this.Manufacturers made to what they thought they should be. Muzzleloader rifles area good example of this ,I have seen them real deep and other brands of same caliber really shallow.

    I have a good friend who is a retired gunsmith, I'll ask him when I see him next.

    Grahame

  4. #4
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    SAAMI is usually my "go to" for this sort of info

    http://saami.org/specifications_and_...ire.pdf#page=8

    scroll down the page to the .22 section, it has all the standardised specs like bore diameter, groove depth, twist rates, case dimensions..etc, they cover centre fire and shotguns also, it's a great resource for anybody else interested

    Edit: here's their website SAAMI

  5. #5
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    And they are also making barrels with variable twist.
    Some of our top service pistol have twist rates that conflict with the norm...some fast some slow. No rhyme or reason other than getting those ten points or X ring.

    And they swear by it much to the disgrace of the rest of us that struggle keeping all 90 (or 150 if shooting WA1500) within the 7 ring let alone the 9 ring.
    semi auto pistols seem to be where most of the shooters are different from each other. Revolvers are closer to being the almost same
    And as for rifles most agree and settle on the norm

  6. #6
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    Twist rate affects the weight of the projectile that can be used. A heavier bullet requires a faster twist. My 223 Rem has a standard twist (I've forgotten what it is) This gun is limited to about 60gr projectiles from memory. Target shooters often use 68gr or larger. They would need a faster twist.

    Dean

  7. #7
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    Must be a 1/12 twist, my Sako .223 Rem has a 1/8 twist rate and shoots the heavier pills, I'm running 69gr HPBT at the moment but it'll take 80gr no problem

  8. #8
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    Yes, it is 12 or 14 I think. I generally use 55gr HP. I keep thinking about trying bigger pills, up to 60 or 62, but I don't use it much. It mostly gets used to stir up the ants in a 44 full of dirt which has a 1/2" sheet of rubber around the front half. I have markers out to 200m.

    Dean

  9. #9
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    You can test the twist rate of a barrel with a cleaning rod. Gently push a tight patch down the muzzle about three quarters of the way . Then mark the end of the barrel with a piece of tape on the rod. Then pull the rod out gently one full turn shown by the tape orientation . Then measure the distance from the tape edge that previously marked the end of the barrel to the end of the barrel now. If for example you get 14 inches then it's a 1 in 14 twist . One turn in 14 inches .
    Also bullet length is what determines twist rate required , not actually weight , so long lighter bullets can need more twist than a heavier short bullet . Weight is used as a general guide because that's the most common know parameter .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

  10. #10
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    Just out of curiosity, if a rim fire 22 shell is struck from the side of the rim, will it detonate?

    Ken

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    Yes, but not 100% reliably.

  12. #12
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    It will fail to fire more often than it will fire because the priming mixture is not getting a good crush really more of a push . The underside of the rim should be supported by a solid edge and the outer edge crushed down slightly on that . That pinches some priming mixture between the two crush points .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

  13. #13
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    Quote Originally Posted by Retromilling View Post
    It will fail to fire more often than it will fire because the priming mixture is not getting a good crush really more of a push . The underside of the rim should be supported by a solid edge and the outer edge crushed down slightly on that . That pinches some priming mixture between the two crush points .
    The miss firing of a .22 rf could also be caused by a lot of dry firing which puts a small indentation on the face of the breech which also results in what retromilling describes above...no support behind the rim of the case so it missfires

  14. #14
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    My .357 mag lever action rifle seems to be an anomaly. My first loads, factory and handloads, were 158 gn JHP jacketed rounds and gave very acceptable accuracy from its 1 in 26" barrel. One day I changed to 125 gn JHP and found it shot about a 300 mm group at 25 meters!! Experiments indicate that weights above 140 gn in any profile shoot fine, but below that weight the group blows right out, with the slugs veering and tumbling wildly. Makes no sense to me, but that's how it is.
    Combustor.
    Old iron in the Outback, Kimberley WA.

  15. #15
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    It could be related to twist rate or obturation in the bore the heavy bullets resist the powder load more so build up more pressure so that in turn expands the bullet into the bore more for better gas seal and rifling grip. Try a grain or two extra powder with the lighter bullets . Also make sure the bore is not heavily fouled with copper and or lead .
    One of the problems with light short big calibre bullets is that the diameter is getting close to the length of the bullet and with a hollow point the centre of gravity moves back towards the base more making it want to behave more like a ball than a giroscopically stabilized projectile . The base wants to overtake the point . When this happens the twist rate needs to be greater .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

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