Inconsistant cartridge overall length

Discussion in 'The Ammo & Reloading Forum' started by Spanky, Jan 18, 2010.

  1. Spanky

    Spanky New Member

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    Lee Loadmaster press
    Doing all functions seperately. 1)Decap and resize .2) Clean primer pockets.
    3)Check brass for length. 4)Prime brass. 5)Hand load powder. 6)Seat bullets.

    COAL range 2.790 to 2.805, shooting for 2.800.

    Is this typical? What to do?
    Is a single stage press more consistant?
    How much will this range of variation affect my grouping?


    So many questions and new ones all the time. No wonder this is so much fun.
  2. JLA

    JLA Well-Known Member

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    is your caselength uniform? Are you crimping? what bullets are you using?
  3. Spanky

    Spanky New Member

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    Just check length to see if the need trimming, but seem pretty consistant.
    308 cal, 168 Sierra MatchKing. Not crimping.

    thanks
  4. Gearheadpyro

    Gearheadpyro New Member

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    Are you measuring to the bullet tip or to the ogive? Measuring to the tip will give fairly substantial differences in C.O.L., your best bet is to pick up something like the Hornady bullet comparator to measure C.O.L. with.

    Also make sure you are seating your primers below flush with the case head, I had issues with that for a while.
  5. 312shooter

    312shooter Active Member

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    What is most important is the ogive and its' consistency in seating and relationship to the rifling. Only measuring with a comparator will tell you this. Measuring OAL is going to be ballpark when using the tip of a bullet as reference,and a caliper. There is slight variance in the manufacturing process and I'm pretty sure thats where you are seeing your OAL difference Not to worry you are probably right on the money with seating, however, buy a comparator if you are an accuracy buff, it will help you along in your pursuit of one hole groups!


    PS stand a bunch of your bullets on a flat surface in a straight line and hold a flat edge accross the tips this will simplify my whole explanation.
  6. medalguy

    medalguy Member

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    That's not much variance, and minor case length variance won't really affect COAL since that is determined by seating depth. What is most likely happening is the ogive of the bullet has a little variance on the curvature and the seater plug is trying to seat all the bullets to a constant depth, but if the shape of the ogive varies just a little bit, the plug will actually seat a little deeper or shallower according to the bullet.
    Are all the bullets from the same lot? I've found that frequently different boxes will be from different lots and the overall shape of the bullet will vary from lot to lot.
  7. Spanky

    Spanky New Member

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    As you guessed, I am measuring to the bullet tip with calipers.
    I will add the comparator to my wish list.

    Thanks all, I feel better now.
  8. JLA

    JLA Well-Known Member

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    gearhead nailed it. the tips are not created equal on HP rifle bullets;)
  9. gazzmann

    gazzmann New Member

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    Shoot 'em and give then a try. HP's do vary.
  10. old semperfi

    old semperfi New Member

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    i live in southern indiana,old country boy at hear
    as far as range variations,there are a few questions?what method do you use to measure powder,i use both a pact electronic and chk that with a balance beam type scale.i also use a lee hand primer,i think i get a more consistant seating when feeling the primer seat in my hand.i am a little anal in this seeing how i load for a few tactical rifles.i hope this helps instead of confuse. old semperfi
  11. rocklinskier

    rocklinskier New Member

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    I haven't messed with loading rifles yet, but will be at some point. Rookie question:

    What is 'ogive' ??
  12. Gearheadpyro

    Gearheadpyro New Member

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    The term ogive refers to the curve of the bullet from the max diameter to the bullet's point. It is a much more consistent measurement than the overall length of the bullet from base to point due to bullet tip variations.

    To measure to a bullets ogive you will need a tool like the Hornady or Sinclair bullet comparators. These measure to the same spot on the ogive of the bullets. As these tools are not yet standardized you can not compare C.O.L.'s measured with a Hornady tool to those measured with a different tool. The reading will likely be different.
  13. Terry_P

    Terry_P New Member

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    +1 That is what came to my mind.
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