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When do you trim your cases

Discussion in 'Ammunition & Reloading' started by pinne65, Jan 4, 2014.

  1. pinne65

    pinne65 Hillsboro, OR Active Member

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    I reload 45/454 but mostly 10mm. I have trimmed 45LC cases once. It was when I reloaded some brass that came from a batch of cheap loaded ammo that I bought. After a couple of firings and resizings case length difference could be measured in 1/100". I have since scrapped that batch and now exclusively use Starline brass.

    Now I have one batch of Starline cases that's been fired twice and one brand new batch. The fired brass measure between .9825" and .9850". The new brass measures .9850 - .9880. I sampled about 5% of batches.

    I don't know how accurate my cheap digital caliper is and I'm also not sure that I'd be able be any more accurate with my trimming lathe.

    Any 5 cents welcome.
     
  2. saxon

    saxon springfield Active Member

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    need to know is this for 45acp or 10mm? if for 10mm
    Lyman lists
    Trim to case length,.989"
    Max.COL, 1.260 " Min. ,1.240

    Sierra lists
    Trim to case length, .987"
    Max. COL, 1.260"

    Speer lists
    Trim to case length, .982"
    Max. COL, 1.260", Min.,1.240"
     
  3. pinne65

    pinne65 Hillsboro, OR Active Member

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    Yep, in this particular case it's 10mm. But I wasn't looking for the trim to length. But rather how much difference in case length you allow in a batch. I would definitely trim if the difference could be measured in 1/100s". But so far I haven't trimmed if it's around 5/1000s". I've kind of considered that to be within the margin of error.
     
  4. saxon

    saxon springfield Active Member

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    ah ok then since max. case length: 0.992"; trim-to length: 0.982 (think 45 acp)
    45 acp Speer manual says trim length for .45 ACP is 0.888 max is 0.898
    so since it head space's on the mouth unless you are going for compitition with in the range of .992 to .982

    i know i can shoot 45acp a boat load of times and still have the brass within the max/min,
    i have been reading alot on 45acp head space and each chamber and how the bullets seats etc etc etc
    so for plinking withen the max/min is fine///// .992 being no more space between the case and bolt face
    .982 being .010 between case and bolt face +- .002
     
  5. Twodogs

    Twodogs portland Or Active Member

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    I never have trimmed my 10MM cases matter of fact I don't trim any pistol cases.
     
    Classic, SPU, stavros4570 and 3 others like this.
  6. Papercidal

    Papercidal Vancouver ,Wa Active Member

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    Most people don't trim pistol cases at all with the exception of magnum revolver rounds that need a heavy roll crimp.
     
  7. Mikej

    Mikej Portland Gold Supporter Gold Supporter 2015 Volunteer 2016 Volunteer

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    I found that roll crimped rounds .38sp, .357, .44 mag/spec and any other, really need to be trimmed to within about .003 to get a consistent crimp. I learned the hard way with very light roll crimps and partially folded brass with .38sp.

    I don't measure taper crimped brass, only do some spot checking.

    Mike
     
  8. SPU

    SPU Southwest Oregon Old Fart

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    I stopped worrying about pistol brass (including crimped brass) after I went through 3000 used .38 special and .357 magnum range pickup cases I bought. I measured every one and none needed trimming. Neither had any of the brass I had fired at least 4 times.

    I asked a buddy about this issue who has been reloading pistol brass 39 years, and was a successful competitive pistol shooter for a decade. He said neither he nor his friends ever bothered trimming because even magnum brass will show signs of splitting at the mouth before it needs trimming, and accuracy was never an issue.

    So I don't trim or even measure. I watch like a hawk for used up brass though.
     
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  9. pinne65

    pinne65 Hillsboro, OR Active Member

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    Sweet - thanks for the input everyone!

    I wasn't really looking forward to hand trim some 2000 cases ;-)
     
  10. RVTECH

    RVTECH LaPine Well-Known Member

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    I too came to this conclusion not quite 39 years ago - but not far behind. However I do check and trim rifle cases every time.
     
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  11. Backfire

    Backfire Tualatin, OR Active Member

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    I rarely have to trim my .38 Special and .45 ACP cases, but I routinely check case length on a gauge because I want consistent crimping. I taper crimp the .45 ACP and 9x19mm cases, but roll crimp the .38 Special/.357 Magnum cases. Many of my cases are given to me by friends who own similarly chambered sidearms but don't reload, so I strive for consistent case length.