Rate of twist

Discussion in 'Reloading' started by chain, Nov 17, 2005.

  1. chain

    chain Well-Known Member

    Messages:
    366
    Joined:
    Dec 28, 2004
    Should the rate of twist of your rifle be a factor in what weight of bullet you shoot? More twist, more weight? I think my .300 win is 1 in 10". Does that sound right for a factory Savage barrel?
     
  2. zingdingo

    zingdingo Well-Known Member

    Messages:
    241
    Joined:
    May 27, 2005
    chain,

    Every 300WM on Savages website I looked at listed a 1-10 twist, so you it sounds like your right on there.

    What the rate of twist practically does is to limit how heavy of bullets you can shoot, for stabilization reasons. You can shoot light bullets in a slow twist or a fast twist, and while they may be slightly "overstabilized" this has no dramatic ramifications. Heavy bullets will only stabilize in a fast enough twist, if it is too slow, you won't stabilize them and accuracy will suffer, possibly severely.

    If you have a faster twist than you need it could cost you some velocity compared to a barrel of slower twist, but this is a relatively minor effect, and normally only something to be considered if you know exactly what bullet or what range of bullets you plan on shooting when ordering a barrel.

    With a 1-10 twist win mag you should be able to use pretty much any commercial bullets, up to and very likely including the 240 gr SMK's. So you don't have much to worry about regarding twist vs. bullet weight with your set up, assuming that you will stay within the readily available commercial bullets.

    I should mention that velocity is also a factor in stabilization. The faster you drive a bullet the more likely it will stabilize for any given set of conditions. I have also heard that it is actually the bullets bearing surface length that matters and not its weight (they are inherently related) but I don’t know much more than that.

    Good luck and good shooting,
    Carl
     

  3. abinok

    abinok Writers Guild

    Messages:
    877
    Joined:
    Nov 25, 2004
    My factory savage barrel shoots bullets that range from the 90gr hornady XTP, and 110 V-max to the 220 and 240gr Sierras very well. Don't worry about twist rate as much as ballistic performance, and in hunting situations terminal performance and you will do just fine.
    1:10 + 300WM will stabalize the 240 SMK under most reasonable situations.
     
  4. bailey1474

    bailey1474 <strong>SPONSOR</strong>

    Messages:
    1,922
    Joined:
    Dec 7, 2004
    Thanks for those 240s abinok /ubbthreads/images/graemlins/grin.gif!!! They stabalize in my 10 twist 300 RUM just fine as well. After shooting a .269" group @ 100 yds, I'm anxious to try it at longer ranges.
     
  5. abinok

    abinok Writers Guild

    Messages:
    877
    Joined:
    Nov 25, 2004
    Glad to hear it Bill! Bumping the quarter minute mark will certanly make them worth some investigation. Are you driving them fast enough to be able to see a advantage over the 220s or 210 class bullets? Oh and how did the pressure trace do?
     
  6. bailey1474

    bailey1474 <strong>SPONSOR</strong>

    Messages:
    1,922
    Joined:
    Dec 7, 2004
    I'm pushing them @ 2850 fps. I haven't run the numbers to see if there is any real advantage over the lighter bullets. I may not mess w/it since this thing is shooting so good. I've got 40 rounds ready to roll and I've ordered some from Sierra and they should be here sometime after Jan. 1.

    The pressure trace deal didn't work very well. When I get time I'm going to contact them and see what I am doing wrong. I don't know if I was just lucky or not, but it seems to me that a guy could find the accuracy nodes simply by shooting over a chrono?
     
  7. CPorter

    CPorter Active Member

    Messages:
    27
    Joined:
    Oct 21, 2005
    For the same caliber and construction, the heavier the bullet the longer it is. For this reason most people associate the twist rate needed to stabilze a bullet with it's weight. This ain't always the case. I shoot .243 through a Rem 700 VLS with a 1:9.125 twist. This is good up to 100 grain bullets, of the old styles, ie: pointed soft point and round nose with short tips and lead cores. Bullets like the partition, grand slam, and VLD bullets don't work at that weight. They have a higher copper content and are generally longer. The larger area, particularly around the nose, produces more lift which needs more spin to counteract or the bullet tumbles. Some bullets are a lot heavier and shorter, those that have tungsten cores for instance, and these don't need the higher twist rate to stabilize.