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Thread: Bullet ogive

  1. #1
    Registered User Deerhunter 28's Avatar
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    Bullet ogive

    I was starting a load today for 69 grain SMK.
    My bullet comparator was giving me different ogive lengths for the bullets?
    Can the ogive length vary?
    I know oal length can.
    55 grain V max may vary .002.
    SMK was varying .008?
    Operator error or can ogive vary?


    Thanks




    PSE EVO 57 Lbs.
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  2. #2
    Registered User cgeorgemo's Avatar
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    Re: Bullet ogive

    Ogive will vary try to group them together so you can seat them in batches.
    5 out of 4 people have a problem with fractions...

  3. #3

    Re: Bullet ogive

    Deerhunter, Using a Matutuyo digital caliper (accurate to .0005") and the Hornady ogive comparator, my ogive measuring results for the Hornady 55 gr. V-max (and the 55 gr Nosler Varmint) are about the same as yours. I would speculate this small variance in ogive lengths is probably very typical with all manufacturers. However, even though the ogives differ a little within the batch of bullets they should all seat to the same Base-To-Ogive length when loaded. However, the Cartridge Overall Length within those loads will vary. Cgeorgemo's suggestion about sorting them into different batches for best accuracy is an excellent idea.

    I am still experimenting to determine why the Base-To-Ogive measurement does vary. Is it my Redding or Forster Competition Seating Dies, my Co-Ax press, the very consistent procedures I use, or "other"?

    The experimenting will take about a month but I will post the results when completed.

    I do not know what a SMK is so I cannot provide an opinion about them.

  4. #4

    Re: Bullet ogive

    SMK = Sierra Match King

  5. #5

    Re: Bullet ogive

    Thanks, barrel-nut. I am still unfamiliar with most of the acronyms and abbreviations used in the reloading/shooting/hunting communities.

  6. #6

    Re: Bullet ogive

    I use two comparators to measure the bearing length on bullets. I attach one to the top and one to the bottom.

    Sierra Match Kings vary as much as .02" on their bearing length. And when I started sorting them my vertical stringing pretty much went away.

    Before I started doing this most groups were in the .4" range at 100 yards. Since they have dropped to .3" with some .2" groups.

    Dolomite

  7. #7

    Re: Bullet ogive

    John, I too use both Forster and Redding competition seating dies and often have slight variations in case head-to-ogive length. I notice it especially when seating a bullet into a case that for whatever reason offers more resistance to seating the bullet. When this happens, the length to ogive will be a bit long. If I take the same cartridge and run it through the seater again, usually it will come out the right length. I believe it's either press flex, or that the stem in the die that positions the actual bullet seater flexes some; however this is pure speculation on both ideas. My press is a Hornady with the Lock-and-Load quick change fittings. I have noticed that the lip around the top of the fitting tends to rise up from the top of the press a few thousandths during hard operations such as full length resizing, but not during less strenuous activities like bullet seating. This puzzles me, because there are a half-dozen or so locking lugs on the fitting that would seem to prevent any upward movement. The die can't be pulled upward by hand, but apparently the press can cause it to bulge upward. I hate this because I love the lock-n-load system, as it makes die changing a two second job. But if it is holding me back from making the best ammo possible, I may have to ditch it and upgrade. Been considering a Forster Co-Ax press, but haven't quite been ready to jump...

  8. #8

    Re: Bullet ogive

    John, I just re-read your post and realized that you are already using the Co-Ax press and are still having this problem. I had hoped that switching to a better press like yours would solve the problem, but I guess not. Maybe it is the die that is flexing??? I'm sure someone here will enlighten us. But if you find anything I'd love to hear about it.

  9. #9

    Re: Bullet ogive

    Yes, the measurement can vary, and it doesn't necessarily correlate to bearing length of the bullet ......Here's why:

    When you seat a bullet, the case head is in a fixed position relative to the seater stem, with the ram up. This is a fixed length, defined by your die setup. Also, the seater stem has a fixed inside diameter, so it will contact the bullet at a point on the bullet where the diameter is equal to the stem I/S diameter. The seater stem makes contact with the bullet somewhere on the nose, between the ogive and the tip. Therefore, the inherent variability in the shape of the bullet from ogive to tip , i.e. the realive taper from ogive to tip, is what defines the "depth" of seating. Bullets with low variability in shape from ogive to tip, therefore, will always give a more consistent base to ogive measurement. BUT...that doesn't necesarily mean they will have better bearing surface measurements - they usually do, since the low variability in nose shape is a good indicator of good quality control, but not always.

    There are several ways the bearing surface length can be equal, but can place the ogive at different points on the bullet. A bullet can have a shorter boattail or a longer boattail section and still have equal bearing lengths.

    Another tip on using the Forster Co-ax - it helps to hold the case against the bottom plate when you start your downward stroke of the press handle. The sliding jaws can some times tilt or elevate the case a little as they pick up and center the case in the jaws. I first noticed this while using an expander mandrel - if you don't hold the case flat to the bottom plate, sometimes the edge of the case mouth contacts the end of the mandrel. When held firmly downward, this symptom dissapeared....and no, that press won't flex.
    Elkbane
    Ecclesiastes 10:2 (NIV) "The heart of the wise inclines to the right, but the heart of the fool to the left".

  10. #10
    Registered User Deerhunter 28's Avatar
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    Re: Bullet ogive

    What I did in this situation was took the longest SMK I had I think .151 don't have number near me.
    I based my maximum cartridge OAL on this bullet.
    So when I load again I will try and find another bullet that same length and go from there?
    Is this a correct way to handle this?

    Thanks


    PSE EVO 57 Lbs.
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    Evo 6 Blacked out 57 lbs.

  11. #11
    benfranklin
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    Re: Bullet ogive

    from my own testing I found there is no way you can
    get the correct ogive length with a comparative tool.
    The reason being,all of your bullets have to be the
    same length in order to do this or you have a bushing
    made that will fit your die.The bushing will rest on the
    ogive there by giving you the closest possible o a l....
    I pretty much gave up on it for awhile until I had
    done some serious thinking about it..You need to
    have the bushing made to replace the seater plug
    that is already in the existing die..This is about the
    only way you are even going to come close to the
    same measurement every time....Good luck...John

  12. #12

    Re: Bullet ogive

    Deer hunter,
    My point was that if you have alot of variability in the bullets themselves, it will show up in your base-ogive measurements. There's no way around that. And just sorting by bearing surface may or may not fix your seating depth measurement issue. Your targets will tell you whether the variability you are seeing in your measurements are meaningful. I've seem some bullets that were pretty jump tolerant and others that were really sensitive to seating depth. With the type of variability you are seeing, I'd be seating either jammed hard (like 10 thousands plus) or well off the lands. Right at the lands would be pretty iffy if you have a +/- 8 thousands effective seating depth variation........

    I'm not shooting much 22 cal stuff right now (except for ar-15 plinkers), but when I was, I shot Bergers and they shot great. I do know that in the 6.5MM stuff where I've been sorting and measuring ALOT of bullets, the Bergers (130's and 140's) and Lapua Scenars (123's) had the least amount of variability. Lapuas were the best and Bergers were right behind them. I just load them and shoot them. Last time I shot alot of SMK's, they were 130 grain 7MM bullets in a 7mm-08 tactical rifle. As I recall, they had pretty high variability - shot OK, but not truly great.
    Elkbane
    Ecclesiastes 10:2 (NIV) "The heart of the wise inclines to the right, but the heart of the fool to the left".

  13. #13

    Re: Bullet ogive

    Gentlemen all, it seems to me that Elkbane and benfranklin have clearly defined and focused precisely on the problem-which appears to be within the seating die itself and specifically the shape of the seating mandrel and where it contacts the bullet at or forward of the ogive. This statement is NOT intended to cast a doubt on the excellence of both the Redding and Forster Competition Seating Dies; but rather to show that the problem involves many variables i.e.- very minor length differences even within the same batch of bullets and different bullets of different shapes from different manufacturers. I am expecting these excellent dies with only one mandrel with an unchanging shape to neutralize these many variables. I should be happy with the results I have been achieving.

    Dolomite and deerhunter seem to have a good solution-group bullets by "measurement". Sort similar bullets into separate groups and load them as a group to achieve more consistent base-to-ogive lengths and increased accuracy on the range.

    Benfranklin's recommendation to have the die manufacturer make a custom mandrel for each your bullet shapes would also increase consistency of the base-to-ogive length measurement. This involves sending one each of your various bullets to the manufacture and paying for the custom mandrels.

    Elkbane, I have already accidently discovered the necessity of making certain the case is properly located within the moving jaws of the Co-Ax press. Necessity quickly became the mother of invention. And, I agree, the Co-Ax press does not bend or distort in any measureable way during any of the reloading steps. Another thing I noticed about the Co-Ax jaws is the importance of cleaning (just a quick wipe with a clean cotton cloth about every ten rounds) the bottom surface of the jaws so the case is not elevated by particles of dust, etc.

    Thank you all for the help and I will let you know how my various experiments work out. I am already modifying my reloading bench to fit in the Redding Big Boss II press which should arrive tomorrow. I will then reload a number of ten-round batches on each of my three presses after I have sorted bullets by length. The press should have no noticeable affect on the consistency of the reloads.

    This will be a heck of a lot of fun. Should keep me busy and out of trouble (and probably will initiate a short stay in debtor's prison).




  14. #14

    Re: Bullet ogive

    Quote Originally Posted by Elkbane
    The seater stem makes contact with the bullet somewhere on the nose, between the ogive and the tip. Therefore, the inherent variability in the shape of the bullet from ogive to tip , i.e. the realive taper from ogive to tip, is what defines the "depth" of seating. Bullets with low variability in shape from ogive to tip, therefore, will always give a more consistent base to ogive measurement.
    Elkbane
    Thanks elkbane. You have hit the nail squarely on the head. This makes our problem completely understandable. Frankly, I'm a bit embarrassed that I never thought about that until now. You probably saved me about three bills for the new press I now won't be getting.

    Never underestimate the collective wisdom of the Brotherhood of the Barrel Nut !

  15. #15
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    Re: Bullet ogive

    Yes, kudos to elkbane for his spot-on explanation. It is this reasoning that leads me to believe that seating dies could be much improved if seating plugs were cut to make contact on the ogive just barely above the bearing surface. No other point of contact. It seems this might eliminate the need for seating plugs cut expressly for a given bullet shape........... I've tried to make plugs for specific bullet shapes using epoxy in the plug. For the reasons elkbane expressed this didn't work :D..... While we're on this subject I thought I'd advance the wider seating plug idea to see what others thought. Anyone care to comment? I'm a pretty thick skinned old coot so you won't hurt my feelings if you call me stooopid ;D

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