Page 1 of 2 12 LastLast
Results 1 to 15 of 19

Thread: Twist Rates?

  1. #1
    Join Date
    Mar 2007
    Posts
    52

    Twist Rates?

    As some of you know, Iv posted some questions here before. I am puzzled about these rate of twist on some of the rimfires. 16 twist has been the norm for rimfire but , there must be some advantage to 17 and 17 1/2. would somone please enlighten me on this?

  2. #2
    Join Date
    Feb 2003
    Location
    upstate, N.Y.
    Posts
    2,711
    The thinking is that they are less affected by wind.

  3. #3
    Join Date
    Mar 2007
    Posts
    52
    Thank You Tim. Now...I may be thinking wrong, but, wouldnt you have to shoot a little faster FPS with a 17 to 17 1/2 twist to insure bullet stability?

  4. #4
    Join Date
    Feb 2003
    Location
    Pine Bush NY
    Posts
    861
    Here's the deal with the slow twists. If you live up in the North, avoid the slower twists, as the bullets tend to be unstable in the cold (yaw). If you live in the warmer South, they should perform very well for you. You shouldn't worry so much about the bullet speed, those numbers marked on the boxes don't mean much really. I've had rifles with 16" 16.5" 17" and 17.5" twists, I prefer the 16" or 16.5" twist, but I live up North.

  5. #5
    Join Date
    Feb 2003
    Posts
    174
    No just have warmer temps. This is not true for all, always exceptions, but 16 twist shoots pretty good in all conditions with a variety of standard velocity ammo. 17 twist shoots better in the wind. But 17 sometimes has stability problems in colder weather (35 degrees for mine might as well throw rocks). I got 17 twist because here in Kansas we have lots of heat and wind. But our early matches in April I might as well not show up. Perhaps a 17 twist might shoot better in cold weather with higher velocity ammo such as biathlon. I don't think there are any concrete rules when it comes to rimfire though. Rich

  6. #6
    Join Date
    Feb 2003
    Location
    upstate, N.Y.
    Posts
    2,711
    Quote Originally Posted by 2Dogs View Post
    Thank You Tim. Now...I may be thinking wrong, but, wouldnt you have to shoot a little faster FPS with a 17 to 17 1/2 twist to insure bullet stability?
    No. It's not slow twists that have caused bullet instability as much as rifling configuration.

  7. #7
    Join Date
    Feb 2005
    Posts
    482

    Tim...

    No. It's not slow twists that have caused bullet instability as much as rifling configuration.

    Can you expand on this a little bit?

  8. #8
    Join Date
    Feb 2003
    Location
    upstate, N.Y.
    Posts
    2,711
    The short answer is that certain configurations have tended to have a few more out of round bores than others, and frankly a tenth or two out probably is more a culprit than twist rate.

  9. #9
    Join Date
    Feb 2003
    Location
    Pine Bush NY
    Posts
    861
    Just wondering. If the culprit is an out of round bore, why would such a barrel shoot great on hot days and yaw like a crazy on the cool days? I would think an out of round bore would just plain shoot poorly all the time. I had a 17.5 twist barrel that shot great in the couple hot months that we have here and was unstable when the temps got below 50. I would think that if a barrel maker is making out of round barrels, it would be so for all the different twist rates that they make. My experience was (and I think it was the same for others), same barrel maker, faster twist, problem solved.

  10. #10
    Join Date
    Feb 2003
    Location
    upstate, N.Y.
    Posts
    2,711
    Different buttons, first of all. 17 1/2-18 twist is about the edge of stability to begin with. Why do YOU think the guys with the same twist in a 6-groover did'nt suffer much in the way of instability? Faster ammo reduces the effect somewhat.
    Last edited by tim; 06-18-2009 at 04:47 PM.

  11. #11
    Join Date
    Feb 2003
    Location
    Pine Bush NY
    Posts
    861
    >>>"17 1/2-18 twist is about the edge of stability to begin with".<<<

    Sooo, you're saying it is the twist rate that caused the instabililty. We have reached agreement. I guess.

    >>"Why do YOU think the guys with the same twist in a 6-groover did'nt suffer much in the was of instability? Faster ammo reduces the effect somewhat."<<

    The 17.5" twist barrel that I had was the 6 groove so, no, I don't think that.

  12. #12
    Join Date
    Feb 2003
    Location
    Pine Bush NY
    Posts
    861
    Ok, in the interest of accuracy, Tim, we are sorta both right and wrong. Thanks to posting here, I received a phone call and have learned "The rest of the story".

    The deal with the bullet instability and twist rate, is that it was the combination of a real tight barrel choke and the slow twist that was the problem. It resulted in the bullet elongating such that a slow twist could not stabilize the bullet. There have been slow twist barrels that shot well in the cold north and could stabilze a bullet, but that weren't elongated by too much choke in a the end of the barrel. I hear that the problem has been corrected and if one wants a slower twist barrel, you should be OK. There are now some 17" twist barrels shooting very well up here in the cold.

    See, sometimes this forum can be useful.

  13. #13
    Join Date
    Feb 2005
    Posts
    482

    To Bill B...

    resulted in the bullet elongating

    I take this to mean the decrease in diameter was added to the length. Most "chokes" might add about .0005 to bullet length. Is this roughly the number we should be looking at as having an effect on stability?

  14. #14
    Join Date
    Feb 2003
    Location
    Pine Bush NY
    Posts
    861
    Quote Originally Posted by pacecil View Post
    resulted in the bullet elongating

    I take this to mean the decrease in diameter was added to the length. Most "chokes" might add about .0005 to bullet length. Is this roughly the number we should be looking at as having an effect on stability?
    Yes, that's what I mean. I don't know the answer to your question, as I didn't get into those specifics in my conversation. My understanding is that the reason for the problem was discovered to be a combination of slow twist and a tight barrel/choke and the new slow twist barrels shouldn't have the same problem, as they are not as tight. The best bet, if one is considering buying a barrel, is to talk to the barrel maker and gunsmith and discuss the matter.

  15. #15
    Join Date
    Jan 2009
    Location
    Elizabethville, Pa.
    Posts
    183

    The thinking is that they are less affected by wind.

    O GREAT ONE I DONT BOW TO YOU!

    And no, I will not shut up
    ?


    Howard E. Newman Jr.

    AKA pickles
    Semper fi

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •