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Thread: Will a 1 in 12" twist rate stabilize a 30 caliber 220 grain round nose?

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    Member mainer_in_ak's Avatar
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    Default Will a 1 in 12" twist rate stabilize a 30 caliber 220 grain round nose?

    I've always wondered if anyone has tested a 220 grain roundnose in any 30 caliber rifle with a 1 in 12" rifling twist. I'd imagine that it should be able to stabilize a bullet out to at least 100 yds. but I don't know for sure because I've never personally tested it.

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    I wouldn't bet any money on it, even if it would fit in a magazine once loaded. Just borrow a hand full from a bud and give it a go. I would think they will make key-holes in your target.
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    What velocity/cartridge are you considering?

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    Member mainer_in_ak's Avatar
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    I'm looking for actual experience with ANY 30 caliber rifle with ANY barrel length shooting 220 grain round nose and what the results were.

    Of course......with a 1 in 12" twist. I might have to give it a try myself since all I've been able to find is regurgitation of assumptions regarding this twist rate, with no actual proof.

    If a 35 whelen can stabilize a 250 grain 35 caliber bullet with a 1 in 16" twist.......I'm getting curious about the 30 caliber with the slower twist.

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    I shoot Hornady 220's out of my Remington 30-06 Baikal double rifle and it has a 1-10. They shoot great.
    Tennessee

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    Supporting Member Amigo Will's Avatar
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    I have shot 220's out of a Ruger RSI in 308 and they shot OK but not near a nice as 200's
    Now left only to be a turd in the forrest and the circle will be complete.Use me as I have used you

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    Member mainer_in_ak's Avatar
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    Quote Originally Posted by Amigo Will View Post
    I have shot 220's out of a Ruger RSI in 308 and they shot OK but not near a nice as 200's
    Thanks Amigo,
    I thought they would do "OK". For "in your face" kind of work as a bear protection load I'm sure they'd hit where yah aim. I'd like to see ur rifle over a beer sometime when I come down your way.

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    I shoot 200s and 220s almost exclusively out of my old 06. And if I remember right I think the 220 Seirra is about the same length as the 200 Speer Spitzer. I don't know what twist my rifle has, never measured it, it's a factory 4 groove 03 bbl. But I guess the best way to find out would be to shoot some. If your in town I'll give ya 5 of them to try if you want, heck if it's an 06 I'll even give you loaded ammo.

  9. #9

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    Can't comment on 1 in 12 twist, however I shoot 220 grain partitions out of my Tikka with a 1 in 11" twist. They are semi-spitzer tipped. Don't know if true RN are any better or worse in that regard. They shoot GREAT! .9 inch, four shot group at 100 yds. This thread concerns shooting 208 grain Amax and 210 grain Bergers out of a 1 in 12 Rem 700

    http://www.snipershide.com/forum/ubb...1299481&page=1

    Both Federal and Remington load 220 grain 30-06 ammo. Hornady 220 gr RN bullets I think.

    According to an article I read written by Gale McMillan a few years ago, if a bullet is stable 50 ft out of the barrel, it will stay stable as long as it remains supersonic.

    Regards

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    Member hodgeman's Avatar
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    My Kimber .308 with 1:12 twist would not stabilize 220s and was somewhat marginal with 200s. It had a real preference for lighter bullets but shot 180s OK.

    I gave up after one brief period of heavy bullet experiments, I might have been able to work with them some and get decent results.

  11. #11

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    Mainer, the biggest factor in a bullet's twist requirement is it's length. Velocity will help a little. If you take a look on Bergers web site at the 210gr 30 cal VLD, they list a required twist of 11. I have shot those bullets out of my Sako 300 WSM 11 twist from 2600 - 3000 fps and they have stabilized fine. They are 1.48" long which I'm guessing might be a little longer than your round nose. The 190 VLD's are listed as needing a 12 twist. You're probably on the edge with the 220's depending on how long they are.

    http://www.bergerbullets.com/Product...20Bullets.html

    That being said, the stability factor required for terminal ballistics will be higher than the SF required for paper punching, meaning, there's a good chance your bullet will start to tumble on impact, especially at closer ranges because the required terminal ballistic SF goes up the closer you get to the muzzle. Reason being the bullet is spinning at the same rate once it comes out of the barrel through the duration of its flight and the slower it goes the greater its rate of spin per distance traveled.

    In short, I probably wouldn't recommend in your face work for a 220 bullet coming out of a 12 twist if you want predictable and reliable penetration.

    -Mark

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    'the biggest factor in a bullet's twist requirement is it's length."

    Yep. 30 cal 220 grain partitions are 1.37 in long. 200 grain partitions are 1.35 in so not much difference. 180 grain E-tips are 1.464 in long, and 210 Bergers are slightly longer at 1.48 in. Amazingly, 165 grain Barnes solids are slightly longer than the 220 gr partitions! Nobody seems to think they are too much to stabilize in a 30 cal 1 in 12 twist.

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    Sponsor ADfields's Avatar
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    Quote Originally Posted by cessna308 View Post
    'the biggest factor in a bullet's twist requirement is it's length."

    Yep. 30 cal 220 grain partitions are 1.37 in long. 200 grain partitions are 1.35 in so not much difference. 180 grain E-tips are 1.464 in long, and 210 Bergers are slightly longer at 1.48 in. Amazingly, 165 grain Barnes solids are slightly longer than the 220 gr partitions! Nobody seems to think they are too much to stabilize in a 30 cal 1 in 12 twist.
    I thought the important stabilizing factor was the gyroscopic action of centrifugal force applied from rotation speed, RPM. How fast it needs to spin would be affected by the distribution of mass within the shape. I suspect a solid (copper/lead/other) would have a more efferent distribution of mass than a lead core with a jacket so assuming same shape would stabilize at lower RPM. I know when designing a flywheel (which uses centrifugal force to store energy) you want it center light and edge heavy not the other way around like a jacketed bullet. Extra weight in the center is counterproductive to a flywheel so I would think same is true of a bullet . . . itís reducing the mass-diameter if that makes any sense.
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    Quote Originally Posted by cessna308 View Post
    'the biggest factor in a bullet's twist requirement is it's length."

    Yep. 30 cal 220 grain partitions are 1.37 in long. 200 grain partitions are 1.35 in so not much difference. 180 grain E-tips are 1.464 in long, and 210 Bergers are slightly longer at 1.48 in. Amazingly, 165 grain Barnes solids are slightly longer than the 220 gr partitions! Nobody seems to think they are too much to stabilize in a 30 cal 1 in 12 twist.
    A 308 can push a 165 grain Barnes at much higher velocity than a 220 grn NP. This velocity increases the rotational forces which are imparted by rifleing, creating stabile bullet flight. If a 308 could push a 220 grn bullet at 300 Win Mag velocities it could stabilize it and get proper penetration on impact instead of a "predicted tumble".
    " Americans will never need the 2nd Amendment, until the government tries to take it away."

    On the road of life..... Pot holes keep things interesting !

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    Member mekaniks's Avatar
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    Default Barrel twist by Louis Braun

    barrel twist.jpgbarrel twist pg 2.jpgI ran acroos this article in the Washingtom Arm Collectors mag the other day by author Louis Braun. Its a pretty good article regarding measuring barrel twist and determining optimum twist twist rates based on The greenhill formula. Its four pages and I can only attach 2 at a time so will post again with the last 2 pages... more to come

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    Member mekaniks's Avatar
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    Default Barrel twist- Louis Braun pages 3 & 4

    barrel twist pg 4.jpgbarrel twist pg 3.jpg Here is pages three and four. Anyway, The Greenhill formula works. Bullet diameter squared x 150 divided by bullet length. As an example I have used it for my .338. 225g Barnes bullets. The bullets are .338 diameter and 1.432 long, so .338 x .338 x 150 divided by 1.432 = 11.9 or an optimum twist of pretty close to 12". My gun has a 1:12 twist so it shoots these bullets just fine. Did the same thing with my 185g Barnes bullets and came up with 13.9. Since my guns twist rate is a just little fast it shoots these just as well... so here is some micrometer and calculater fun

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