bullet runout

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by popwarlick, Jan 5, 2009.

  1. popwarlick

    popwarlick Member

    Jan 21, 2008
    I built a tool to check the runout on loaded ammo.Can someone give me the tolerances on bullet r/o and are there any other tolerances i need to look at.THANKS TERRY
  2. Mikecr

    Mikecr Well-Known Member

    Aug 10, 2003
    First, your terms seem off.
    You will not measure bullet runout, because there isn't any.
    Your tool will likely measure case runout, and/or loaded ammo runout, off the case shoulders, or mouths, or off the bullet bearing or nose.

    A standard for runout measurements(in my view) is Sinclair's. You set the case on bearings between the web and shoulder. While rolling the case, your measure in runout is read from an indicator you set on the round. The runout seen will grow from shoulder to the bullet tip.
    The case head rides against a peg to prevent for/aft movement while rolling, and many use an eraser to roll cases with less error in measurement(due to slightly rocking the case off the bearings). This is where bearings are better than V-blocks.
    I consider Sinclair's the standard because any runout in loaded ammo will atleast show up using this tool. In fact, it either shows runout as it is, or else amplifies it beyond what it is. Depends on what you specifically measure & where, and what is causing the variance.. But no irregularity gets by unnoticed.
    It doesn't mask runout like the bullet straightening types out there. These support loaded rounds by the ends only, measuring nearest one end, while allowing the majority of runout(caseborn) to swing in the wind -unindicated.
    While you can measure runout quit low with these, drop em on a Sinclair to see what you really have left.

    Do you have a pic of your tool?

  3. britz

    britz Well-Known Member

    Mar 11, 2007
    IMHO, you need a guage that will measure to the nearest .001". I Jerry riged a simple and workable (however crude) runout guage using an old caliper, 4 quarters, epoxy, screws and a few pieces of scrap wood. I started using the caliper that I had and simply installed it on the jig when I wanted to try to measure some runout. A couple months later, I dropped the caliper and I noticed problems with the threads on the caliper right where I needed it to measure a 300 wsm cartidge and I had to replace it so I used that one to perminantly mount on my jig. A caliper is $30 so I wouldn't recomend doing this if you have to purchase a caliper for that specific reason - just get a RCBS guage for $70 and be done with it.

    This thing works well enough for me ;)

    I'll attempt to download a picture of my little piece of cra..... "art" ;)

    Last edited: Jan 6, 2009
  4. kraky2

    kraky2 Well-Known Member

    Jan 6, 2005
    There are all kinds of feelings about what bullet runnout does to the accuracy of a rifle.
    I would submit the following and I'm sure I will be corrected quickly....

    For the average hunting rifle for out to 300/400 yds shooting:
    Match grade is under .003" total runnout.
    average ammo under .005" runnout.
    getting bad .005-.007 runnout.
    bad over .007" runnout.

    For the long range and benchrest crowd.
    Match grade is under .001" runnout.
    Average is under .002" runnout.
    Getting bad is .002-.0035
    bad runnout .0035 and over.

    Also remember that the average hunting rifle has a chamber that is much looser than a match grade rifle and even .001" runout will probably not get you perfectly aligned with the bore of your barrel.
    The match grade rifles are aligned perfectly and have chambers that do hold perfect ammo in near perfect alignment.

    I would also venture to say that a high quality match grade rifle shooting .006" runnout ammo will probably outshoot a decent factory rifle shooting .001" runnnout any day of the week.

    These are really vague statements and based on my admittedly biased opinions!