Why can't i reload exact cartridges?

Discussion in 'Reloading' started by Dom, Feb 13, 2019.


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  1. Dom

    Dom Active Member

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    As the Title suggests, I find it almost impossible to load cartridges that are all exact. I understand there are so many variables it is impossible, but something has been bothering me for years. Let me see if I can explain what I'm trying to say here, and it has to do with the measurement of a loaded round, namely, off the Ogive.

    A few specifics, this caliber is 6,5 x 55 but applies to any. Bullet is 130gr the Nosler Accubond. My press is a Foerster Co-Ax, and the Die is RCBS Comp Micrometer Bullet Seater. I am using a Stoney Point Comparator (now Hornady LnL), with the 6.5 insert.

    Here is what I'm looking for:
    [​IMG]

    Many do measure exactly 2.530, however I always get a few off, mostly under, and I have learned when all adjustments are set, not to touch and play with adjustments, because that seems to make it worse. If one measures simply to the point of the bullet, you will have variances. But how can it vary measuring to the Ogive?

    [​IMG]

    Ok, close enough, or is there some reason I just can't get 100% of my loads to measure exactly the same? I have not touched anything, how can the measurement possibly be different? This has had me stumped for years, as I have no logical explanation how the measurement can be different.
     
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  2. Brado16

    Brado16 Well-Known Member

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    Is it possible some of the bullets tips are hitting the "wall" on the inside of the red comparator? If so, can you loosen the allen set screw and pull the 6.5mm bushing out a little, retighten, and then try measuring again to see if you get the same results?
     
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  3. Rick Richard

    Rick Richard Well-Known Member

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    Measure just the projectile from its base to the Ogive. You might find that is the culprit. I have found that bullet dimensions vary.
     
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  4. Rflamm250

    Rflamm250 Well-Known Member

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    I have found this usually is related to neck tension. Example: a piece of brass with less neck tension will result in the bullet being seated deeper than those with slightly more neck tension. If you have ever used an arbor press to seat bullets you can really feel the difference in neck tension. I can usually tell if a loaded round is going to measure slightly long or short by the feel before I ever measure it.
     
  5. dok7mm

    dok7mm Well-Known Member

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    Most of the variance is in the bullet, but some can be in your seater stem and in your case necks. Sorting your bullets by base to ogive will give more consistent bto on loaded rounds.

    The higher quality bullets will have less variation, as a general rule, than others. I weigh and sort all the Nosler & Hornady bullets I use, as there seems to be a good deal of variance in lot to lot and even in one box. It all depends on how far down the rabbit hole, you want to go.
     
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  6. cohunt

    cohunt Well-Known Member

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    Like post #3 says, bullets differ. Your seating system does not seat the bullet by seating off the ogive, it uses an arbitrary point much closer to the tip.

    If you were to use a "more exact" bullet -like something like a "hand turned" or match bullet you will see much better results ( I like hammer bullets, they are very exact)

    Other things that can affect it are press/die rigidity and neck tension
     
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  7. okie man

    okie man Well-Known Member

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    If exact dimensions from case head too ogive is what you are after you really have one choice! Seat all your bullets .005 longer than desired. Measure each one and put them into groups from longest too shortest, then go back and adjust your seater die the correct amount too put the shortest group in spec! Continue with each group adjusting the die as you go! Not bad with a micro adjust die! Keep a eye on you’re c.o.a.l if your seating real close mag box maximum. I have about 200 308 rounds that will be top of mag box only loads.I went off of base too ogive on a big lot of bullets and the were very different on tip too ogive dimensions. They shoot good though!
     
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  8. RockyMtnMT

    RockyMtnMT Official LRH Sponsor

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    Load density if you are crunching powder at all.
     
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  9. bob4

    bob4 Well-Known Member

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    I have this issue also. I'll get 5 or 6 in a row and I think I'm a machine. Then it happens, next one is .002-.005 under. I just blame it on the bullet and make a quick adjustment for that one, seat it and move on. If they were all erratic I would look further into it. This is where a collet puller earns its keep in my eyes. Just the slightest tug and re-seat. I use all Redding and Forster dies.
     
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  10. bigedp51

    bigedp51 Well-Known Member

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    If the seater plug is only touching the bullet around the mouth of the seater plug it can be forced further down the bullet when seating. If you want more accuracy the die makers can make a new seater plug that is a prefect match to your bullet. Meaning the inside of the seater plug will have 100% contact with the bullet.
     
  11. Dom

    Dom Active Member

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    Great guys, thanks, I got it -- it's all of the above, lol. I do believe it is a combination of things, mostly bullet seater and neck tension. I now see the light where that would affect the results, thank you all for your comments, appreciate it. This particular load is not compressed.
     
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  12. Brado16

    Brado16 Well-Known Member

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    Some seating stems don't work well with VLD bullets. To remedy this you can remove your seating stem and then chuck one of your bullets into a cordless drill. Apply some lapping compound to the tip of the bullet and then hone out your seater stem slightly. This should result in more concentric and even contact between your bullets and seater die.
     
  13. Mikecr

    Mikecr Well-Known Member

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    Wrong. The ogive is the entire nose, and the seater is pressing against it (at generally the best point for pushing a curved object).

    Variance in seating force from seating friction causes the seater plug to wedge against the nose with variance. This, affecting CBTO.
    Ogive radius variance changes the datum your measuring tools rest at.
    Removing excess seating force helps. Qualifying Ogive radius helps.

    Believe me YOU CAN seat every bullet to not only the same CBTO, but to the same land contact relationship as well.
     
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  14. 243winxb

    243winxb Well-Known Member

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    If using a shell holder (SH)? The Redding comp seater is allowed to ligntly touch the SH on seating. Acts as a stop. Removing any slop from press linkage. (Not that yours has slop) Just saying.:)

    The Lee dead length bullet seater also uses the SH as a stop.

    More likely a difference in bullets?
     
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