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Thread: NOW what am I messing up?

  1. #1
    Member 8x57 Mauser's Avatar
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    Red face NOW what am I messing up?

    Yet another load work-up question:

    Shooting strings of 6 shots each with 55.0 and 55.5 grains of powder, I get 2 rounds in each string that chronograph roughly 400 fps below the other four in the string.

    I do not have this problem with other shot strings, from the starting load up to and including 54.5 grains. I do not have this problem with strings loaded with 56.0 or 56.5 grains.

    Groups with the two weird strings (55.0 and 55.5) are roughly 3/4 inch larger than groups with lower and higher charges.

    What in Heaven is going on here? Bad chronograph? Funky primers? My rifle hates the number 55?

    For all loads:
    Win nickle brass - all from Winchester factory ammo, all fired one time through the same rifle used to work up this load. All cases neck-sized with the same die - no adjustments. All deburred and chamfered with the same tool. All brass trimmed to the same length.

    All primed with WLR primers from the same box, seated with the same press.

    All charged with IMR 4350 from the same canister. All charges thrown and then weighed on the same balance, on a wooden surface, without moving or adjusting it. After each charge weight is loaded, the balance is checked for zero, then set to the next charge weight.

    All loaded with 180-grain bullets from the same box.

    The barrel is allowed to cool after every shot. The barrel is cleaned betweeen each string.

    I'm pulling my hair out trying to figure out why there are 4 rounds on my chronograph that don't make any apparent sense. Can anyone explain this to me?

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    Default

    I was using some ball powder and a similar thing happened to me. I don't know the ans but believe it is because some of the powder was not being burned, not enough powder in the case to cause complete burning. It was BLC2 in a 30-06. But that is only my guess. Other may know the answer. J.

  3. #3

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    Are the first two shots in each string the slow ones, or are they scattered through the string? If it was the first two I could imagine it was some weird artifact from cleaning, but by the same token, if they were the last shots I'd imagine it had something to do with fouling buildup. Who knows?


    All idle speculation, because I've never seen anything like it.

  4. #4
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    1st and 3d at 55.0.
    5th & 6th at 55.5.

    Those two strings were fired at separate range sessions a week apart, by the way.

    Loaded on different days, too, come to think of it.

  5. #5
    New member George's Avatar
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    Default uuueee

    400 fps difference! I haven't got a clue. Like OldRgr suggested, if you hadn't said 4350 in a 06 behind a 180 I'd have guessed some really slow ball powder of some kind in a large magnum case with the wrong primer. Is the chrony at least 15 ft. from the muzzle? Just doesn't sound right at all. Might try someone else's chrony if possible- otherwise no help here. Maybe a B&C mosquito thru the skyscreen at the wrong time?

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    Question That sounds interesting

    You sound like a careful and consistent hand-loader, but 400 fps is a significant variation within the same string for the 06. The fact that you have the same pattern in descrepant velocity within the string across two shooting sessions on two different days exceeds the probability of chance variation, i.e., the recorded velocity variation appears to be real and not just a random or chance variation. Therefore, the B&C mosquito theory is out (although I personally like it). If you really have to figure this out (as opposed to simply avoiding this particular load...and just loading below or above it), then I suggest you apply the principle of parsimony, i.e., the most simple explanation is the best explanation. Rule out the simple stuff, e.g., change the batteries in your chrony, double check the distance from the muzzle, fire two different strings from a different rifle/load during the same shooting session as the 06 to check for a similarly anomolous velocity pattern within the string (hence suggesting that your chrony might be dizzy), borrow someone elses chrony to see if the same pattern exists with the 06 load, etc. You sound careful at the reloading bench. Let us know what you find out.

    Doc

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    This has been a weird day for me. I won't go into details but I tried to post a reply to this twice and both times my computer puked.

    I didn't know if your problem involved your going bald or your loading/shooting situation.

    I have never seen in some sixty thousand rounds through a chronograph (actually that's just a guess, it is over forty) a four hundred feet per second spread from one load.

    My guess is you have a bad primer that coincidentally showed up or your powder is wet. (old, caked) If it is ball powder, W760, H380 H414, H450 I'l just tell ya it is the powder. This stuff has bummed me a dozen times and every stinkin' time I swore I'd never use it again. Well finally I have given it up. I guess I still have some down on the farm but I'll give it to my son-in-law to shoot in something. I'll probably have to give him my old 308 to shoot it up.

    I guess the thing to do is do it again and see what happens.

    Doc's mosquito theory is good, when the bugs are out or falling leaves they cause chrony trouble, but this seems so exact and like it was triggered by the bullet. 400 fps wow! I know just go into denial and pretend it didn't happen, and reshoot everything. I've done that a lot. When in doubt, recalculate.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  8. #8
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    Default Parsimony

    I'm going to use that mosquito explanation for shots that fly unexplicably wide of the rest of the group, too. "Pulled it? Heck no! Must've been a mosquito."

    But parsimony is worthwhile. Two folks mentioned distance of the chronograph from the muzzle. To be honest, I haven't measured. What's the ill effect if I've been setting it up 12 feet from the muzzle instead of 15?

    To briefly answer other ideas: the first time this happened I had a second rifle working up an altogether different load. The 6-shot string on that one had an extreme spread of 24 fps and a standard deviation of 9.6. The second time it happened I only had the one rifle.

    I went back to my range notes: The most extreme was just under 400 fps difference. Two of the others were in the 320 neighborhood, and one a hair more than 200fps slow. So I should have started this thread saying they were anomalous by 300 fps, not 400.

    Murphy, I don't know what thinning hair has to do with it, but this weirdness has definitely given me some new gray ones!

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