Bullet runout?

Discussion in 'Reloading' started by Greg Duerr, Apr 2, 2013.

  1. Greg Duerr

    Greg Duerr Well-Known Member

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    So how critical is bullet run out and when does it start to affect goup size. .005 or more? Would it be noticable when shooting at 100 yards............I would guess that all improvment add up to better accuracy but some within themselfs can make a noticable difference.

    Has anyone used the Hornady Concentricity Gauge..........SO, it will eliminate bullet runout? Can it be used to measure case neck runout also?
     
  2. cornchuck

    cornchuck Well-Known Member

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    I bought a Hornady Concentricity Gauge after watching Shawn Carlock use one on his reloading video. Plus I had Cabela points burning in my wallet. I will tell you my groups at 200 yds have shrunk from about 1 inch to half inch. Shawn said .002-.003 of an inch of bullet runout is acceptable but I can get them down to .001 with the gauge. I don't think the gauge can be used to find neck runout. The bullet sits in a indented shaft where you can spin it like a lath.

    Bushing resizing dies are suppose to help with bullet run out. I did buy some from Redding but haven't set them up yet to see if runout is eliminated. Wanted to reload this batch of brass because I already had them resized with my old dies.



    Jason
     

  3. Mikecr

    Mikecr Well-Known Member

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    Your terms here would poison better responses.
    BULLETS, are the heavy pointy things that fly downrange to your targets. There isn't any runout in them practical to measure.
    CARTRIDGES amount to the completed ammo, including all components.

    Cartridge runout amounts to a sum of skewing from loaded case AND seated bullet.
    Cartridge eccentricity represents departure from a centerline(any), rather than departure from straight, or round(runout).
    Concentric means same w/respect to a centerline. A cartridge can 'measure' perfectly concentric while presenting excess runout, depending on the measurement methods.

    Just some things to think over here.
     
  4. Greyfox

    Greyfox Well-Known Member

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    I have been using the Hornady since it was introduced. I really like the gauge, and yes, the straigtening devise will reduce the runout. I prefer to get my set up right from the start so I don't have to use it. I'm don't really know the effect of this but you have to apply a lot of pressure to bullet. I'm not sure whether I'm straightening the neck or cocking the bullet, but my accuracy always seems better if my set up is lined up with less than .003" of cartridge runout from the start. Before I got the Hornady, I used the RCBS for several years. It's trickier to get a good reading but it will also measure the runout of the unloaded case neck in relation to the case body. The nice thng about this capability is that I can see if the case is OK as opposed to the seating process causing runout. Also, I can check the dye for runout, as well as the rifle chamber by measuring a fired case. I have been able to detect dyes that are not straight. The dyes that are straight will produce accurate loads that are as good as the more expensive bushing competition dyes. If the neck size is right, this is a money saver. In my experience, the biggest culprit to runout seems to be excessive pressure to seat the bullet. I also think that runout could be a major issue with factory ammo. I have tested so called "Premium" ammo that produce run outs as high as .007-009". IMO.
     
  5. BrentM

    BrentM Well-Known Member

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    I am with Greyfox on this too. One thing I did start doing is to start the bullet about 25% in the neck and then turn the case 180 degrees and finish the seating. When I put the cartridge in the concentricity guage they are generally within .003 to .005. Some are a dead on. My time spent messing with the guage has been reduced and I look for .001 or less concentricity.
     
  6. ZSteinle

    ZSteinle Well-Known Member

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    My 22-243 will shoot about 1 inch groups at 200 yards with about 7 thous of run out. If I use my hornady tool to straighten up the runout to about 1 or 2 thous my groups will open up to about 2 or 3 inches qt 200 yards. Needless to say I dont straighten them anymore.
     
  7. Greg Duerr

    Greg Duerr Well-Known Member

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    now that just ruined my day............................Just when you thought you fixed the problem you realize that you in fact made it worse
     
  8. Gene

    Gene Well-Known Member

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    One way to improve TIR is to use an expander before you size. (Not the expander ball in some dies.) Sinclair and K&M sell them. Then size with a good bushing die. The shell holder must be correct also.

    Straight neck is critical. As for straightening them out with a tool afterwards, I have heard that it can be done, but the next loading will again not be concentric and the same process must be repeated. Your seater die can be to blame also. The tip of the bullet can touch the seating dome inside the die, and skewer the bullet to the side.

    The very best bet is to use Wilson dies with an Arbor press and you should have no problems.
     
  9. Bart B

    Bart B Well-Known Member

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    I'm convinced that minimal bullet runout is best attained by full length sizing fired bottleneck cases in dies without expander balls but with necks about2 thousandths smaller than a loaded round's neck diameter. Don't set the fired case shoulder back more than 2 thousandths. This centers the sized case neck best on the sized case shoulder and causes minimal neck bending from bullet forces on the unsupported case neck when seating bullets. With cases so sized, most any bullet seater will end up with bullet runout less than 3 thousandths which is good enough for no worse than 3" groups at 600 yards with good bullets, powder charges in great barrels.

    This is for the .308 Win case or any bottleneck case headspacing on its shoulcer; runout should not be more than 1% of bullet diameter.

    If your runout tool does not use the case shoulder at about mid point on it for the front reference, then bullet runout sill be effected by the out of round condition of the case body or the case neck's center offset from the shoulder's center reference. It's the case shoulder that centers the cartridge in the chamber shoulder when the round's fired; the case neck free floats in the chamber neck and touches nothing unless it's off center on the case shoulder.
     
  10. Mikecr

    Mikecr Well-Known Member

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    The best we can do is make STRAIGHT ammo.
    Staight ammo is also concentric.
    But concentric ammo, by this attribute alone, is not always straight.

    And as learned by the former neck-bender earlier, making ammo concentric could be the very worst thing we should be doing.

    To make straight ammo:
    1. Cull by thickness variance
    2. Fireform cases
    3. Minimally size the cases
    4. Minimal mandrel neck expansion
    5. Inline seating of bullets (Wilson)