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Thread: Why not 1/8 twist?

  1. #41
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    I've never heard that bullets have less drag when spun faster. I have heard that, and ballistics programs reflect it, that ballistic coefficient changes dependent of velocity. Some are actually higher at a slower speed.

    The faster the twist, the more spin drift, too.

    I have blown apart modern bullets from too much twist. I did so in a 6mm AI with 75 gr bullets and 58 gr bullets through an 8" twist.


    I've seen plenty of 1:9" work with the TSX. Not saying 1:8" or 1:7" wouldn't work better, but they will work oftentimes.

    Barnes recommends 1:8" or faster for their 70 gr TSX.

    I'll reiterate my above statement. The accuracy if your barrel is rarely the reason a shooter missed his target.

    I've seen guys kick ass with 80 and 90 gr bullets in a 1:8" bolt gun. As in beating guys shooting 6mm, 6.5mm and .308s in long range shooting.

    I'll also point out that my experience shows that 1:7" is not more accurate with 40, 50, or 55 gr bullets than 1:8" or 1:9", of course each barrel is different, but the trend seems the 1:9" is best up to 55 or so, the 1:8 and 1:9s I've got experience with show no difference in accuracy from 60 to 77 gr bullets.

    I would never change from 1:8" or 1:7" to the other if the barrel was performing to my expectations. I currently own about six or seven 1:7", one 1:8" and one 1:9". Why? Quality barrels are usually 1:7".

    If it shoots good, keep shooting it until it's toast. No matter what somebody may say on a forum, the results are on the paper or the varmint fields, etc.


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  2. #42
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    Quote Originally Posted by MistWolf View Post
    Bullet length and shape is more important to determining what RPM is needed to stabilize the bullet in flight than it's weight. The TSX is a solid copper bullet and is longer than a lead core bullet of the same weight.

    Sierra uses doppler radar to measure the ballistic coefficient of bullets in flight. They have found the more stable the bullet, the less drag it has because it has less precession. The Sierra 69 gr Matchking (which is shorter than the 70 gr TSX), was found to have a better BC when fired from a 1:7 twist barrel than anything slower, including the 1:8.

    The biggest problem with faster RPMs is that it's hard on lightly constructed bullets. In the late 60s, my father bought a 22-250 and developed a firewalled load using the Hornady 50 gr bullet, one designed to give explosive terminal performance on small critters at 223 velocities, that pushed it close to 4000 fps. We called it the Blue Streak Express because whenever he fired it, the bullet would leave a faint trail of blue smoke behind it. Turns out Dad was driving that bullet to the point it was on the verge of self destructing from the centrifugal forces. Twist on that rifle was 1:12.

    Today's 22 caliber bullets are made to withstand being shot from the ever popular 22-250 and there is little danger of them coming apart when fired at the reduced velocities of the 223/5.56 even with their tighter twist.

    There are more and more reports from serious shooters showing a trend that the 1:7 twist does indeed have an edge accuracy over the 1:8 at longer ranges
    And i completely understand all that. Some bullets will be more accurate with certain twists. For that matter, some bullets are more accurate with different barrels of the same twist. Just because Sierra reported that their 69gr Match King is more accurate with a 1/7 twist doesn't mean a 1/8 barrel wouldn't stabilize it. I can't talk about this testing because I know nothing about it but if they truly did come to these findings, then I'm going to go out on a limb and say they are talking about minute differences such as shooting a .5 group to a .525 group.

    Lastly, in your original post, you mentioned nothing about the 70 gr TSX being more accurate out of a 1/7 barrel. You said that a 1/8 could barely stabilize it which is just wrong. In fact, I'll tell you how wrong it is. Barnes actually recommends a 1/8 twist for use with their 70gr TSX. Why on gods green earth would Barnes recommend a twist rate that wasn't fast enough to stabilize their bullet?

  3. #43
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    Doesn't seem like a hard concept to grasp here.

    The mission ALWAYS defines the hardware. You want to build a kickass varmint rifle? Here's an answer. 1/8 twist

    Everything else? 1/7. I see absolutely NO need for 1/9, ever. This argument has gone on for decades it seems on this site and TOS and I just don't get it.
    If you are going to be shooting x bullets, get x twist. That's really are there is to know. Why must this BS continue to go on. Everything is a trade off and rarely does one thing do everything perfectly.
    The mission defines the hardware.
    Different mission? Use different hardware.
    Going to shoot varmints and need a tack driver? Use your varmint rifle with it's proper twist for it's proper projectiles.

    But let's piss, moan and argue for another freaking 12 pages and come to the same conclusion we always do.
    Last edited by Brahmzy; 02-16-14 at 13:10.

  4. #44
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    Theron lies the problem. Many, if not the majority of stainless match barrels in medium contour come in 1:8". Why does BCM do this if 1:7" is the universal answer? If so, why?


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  5. #45
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    Quote Originally Posted by tylerw02 View Post
    Theron lies the problem. Many, if not the majority of stainless match barrels in medium contour come in 1:8". Why does BCM do this if 1:7" is the universal answer? If so, why?


    Sent from my iPhone using Tapatalk
    Every single one of my medium profile, stainless "Match" Noveske barrels are 1/7.

  6. #46
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    OJ- Easy there, cowboy. First, you've got me mixed up with somebody else. I never claimed the 1:8 is barely adequate for the longer TSX bullet. Second- you came out & said that the 70 gr TSX being barely stabilized by a 1:8 is flat out a falsehood. Them's strong words. One man's "barely stabilized" is another man's "adequate".

    We know that a 1:7 will perform fine with the lighter bullets because Molon did tests using the scientific method proving they will. We also know that each barrel is a law unto itself.

    Bolt action rifles usually have longer barrels for higher velocities resulting in more RPM as well as allowing for a better fit of the case in the chamber. When comparing the accuracy between an AR and a bolt action, we have to look at all the variables between the two to draw an informed conclusion. There is a reason bolt action rifles dominate certain shooting disciplines.

    You make a good point about the difference in accuracy possibly being small. In some applications, that small amount still gets the job done. In others, it's the difference between scoring and missing.

    Nobody is talking about replacing a 1:8 barrel with a 1:7. The original question is "When I get a replacement barrel, will the 1:8 get the job done?"
    Last edited by MistWolf; 02-16-14 at 13:19.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  7. #47
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    Quote Originally Posted by MistWolf View Post
    OJ- Easy there, cowboy. First, you've got me mixed up with somebody else. I never claimed the 1:8 is barely adequate for the longer TSX bullet. Second- you came out & said that the 70 gr TSX being barely stabilized by a 1:8 is flat out a falsehood. Them's strong words. One man's "barely stabilized" is another man's "adequate".

    We know that a 1:7 will perform fine with the lighter bullets because Molon did tests using the scientific method proving they will. We also know that each barrel is a law unto itself.

    Bolt action rifles usually have longer barrels for higher velocities resulting in more RPM as well as allowing for a better fit of the case in the chamber. When comparing the accuracy between an AR and a bolt action, we have to look at all the variables between the two to draw an informed conclusion. There is a reason bolt action rifles dominate certain shooting disciplines.

    You make a good point about the difference in accuracy possibly being small. In some applications, that small amount still gets the job done. In others, it's the difference between scoring and missing.

    Nobody is talking about replacing a 1:8 barrel with a 1:7. The original question is "When I get a replacement barrel, will the 1:8 get the job done?"
    Yes, sorry I got you mixed up with the guy who said a 1/8 twist will barely stabilize a 70gr TSX. I was just stating that I highly doubt the manufacture of the actual bullet would recommend a twist that barely stabilized it.

  8. #48
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    Quote Originally Posted by Brahmzy View Post
    Every single one of my medium profile, stainless "Match" Noveske barrels are 1/7.
    Noveske does use a lot of 1/7 twist.

    I think what the guy you quoted was getting at is that most other match grade barrels do in fact use 1/8 twist.

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  9. #49
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    Notice that Barnes lists the 1:8 as the slowest twist. That means 1:8 is the slowest twist they claim will stabilize that bullet. That can mean that it's barely stabilizing the bullet at an acceptable level and the 1:9 will not
    Last edited by MistWolf; 02-16-14 at 13:37.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  10. #50
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    And HERE, Sierra states their 52gr HPBT Match projectile should be used with either 1/12 or 1/14 barrels.

    This can go on and on and there are far better threads with far more experienced shooters posting up proof and information on the subject. Experienced meaning they specifically buy barrels and projectiles and shoot 1/4 MOA groups as their result and have tested and vetted every barrel twist with every projectile out there. Just google it.
    Last edited by Brahmzy; 02-16-14 at 13:41.

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