Not all rounds pass the gauge test

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Thread: Not all rounds pass the gauge test

  1. #1
    Senior Member Milspec's Avatar
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    Not all rounds pass the gauge test

    I figured I'd defer to the experts here who have a lot more reloading experience than I do.

    I've been reloading some 9mm and about 35% of the completed cartridges won't go all the way in my Dillon gauge. They stick out a bit. All seem to chrono just fine. If I run the rounds back into the seat/crimp die I can get them to pass the gauge eventually. Some of these rounds take 1 run back up in the press and some take 3. Initially I thought this is due to "belling" or expanding the case mouth too much but I'm not so sure. I've been consistent with the components. Same cases, primers, powder, projectiles etc. Everything chambers 100% and accuracy is great at 21ft from a rest.

    I'm open to any thoughts or ideas. I have another 30 or so pre prepped cases (sized, expanded & primed). I figure I'll run through those and then adjust the expanding die on the next run.

    RCBS Carbide dies if that matters.


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    case length variability would be my guess
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    Senior Member Milspec's Avatar
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    Quote Originally Posted by Friscogunner View Post
    case length variability would be my guess
    Interesting. It's once fired 9mm. Would there be that much of a variance? I haven't heard of too many people trimming pistol brass.

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    I think it is probably from flaring the mouth to much in the resizing. I have had a similar problem in the past and this seemed to be the case.
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    If I encounter reloads like that, I will do the plunk test in the barrel they will be shot out of. If they pass this test, they are good to go.

    Sent from my SM-N975U using Tapatalk
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    --Amegatek
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    Senior Member Milspec's Avatar
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    Thanks, I was just about to ask if anyone had more input before I start cranking them out again. It's just odd that its a fraction of the cases.

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    Depending on your press it may be from overflaring the case, followed by seating the bullet and crimp using same die. Sometime 1 die that crimps & seats bullets do not bring the flare of the case back small enough keeping them a bit larger in diameter than others. Possible solution is to use your seating die just for that purpose only, and then use a sizing/crimping die in the next stage. I do this on all calibers i reload and solves case diameter issues.

    Another issue is your sizing/decrimping die is not a full length sizer. And/or this die is not fully running down the full length of the case. These are 2 issues i have encountered in the past.

    Another issue is you may have mixed brass at different lengths. Even though 9mm usually doesnt give to many issues, but once you start reloading rifle calibers you will see this issue more often of different length cases. Solution to this is to use a length guage and trim longer brass down to same length. Hope this helps a d gives you an idea of what i have encoundered in the past.

    FYI i use progress 3 hole and 5 hole progressive presses.
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  9. #8
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    If the case length isn’t consistent, the flares and crimps won’t be either. Since the round uses the case mouth to seat it’d explain the seating differences.

    my $.02

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