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.308 case trimming?

Discussion in 'Ammunition & Reloading' started by sprink, Dec 17, 2015.

  1. sprink

    sprink Battle Ground, WA Member

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    How important is it. I try to load accurate match ammo but hate trimming cases mostly because I do it by hand with a manual Lyman trimmer. I bought some lapua brass that I trimmed to 2.005" when it was new. Now that I've fired it once and FL resized the brass is now 2.008"-2.013". Is trimming necessary again or should I quit being so OCD? Thanks
     
  2. fxdc

    fxdc Da Valley USPSA, SPEED STEEL, IDPA, 3 GUN

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    I would , hate it . But this almost makes it fun. IMAG0889.jpg
     
    Jethro82 likes this.
  3. gundog10

    gundog10 Member

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    Yes you must trim the cases back to spec. If you don't you are creating a pressure/expansion issue within your chamber. The case must be trimmed in order to allow your brass enough room to expand when fired. What could happen: stuck case, cracked receiver, blind and scarred for life. Trim your cases.
     
    Steve M likes this.
  4. elsie

    elsie Way over there on the left Well-Known Member

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    Usually a reloading manual will specify a "trim length". When the unloaded brass gets to that length, you should trim it back to nominal length. I don't have my manuals handy so I can't say what the .308 numbers are, but they should be right at the beginning of the section of data for that round.


    elsie
     
  5. sprink

    sprink Battle Ground, WA Member

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    I've been eyeing that trimmer for awhile, I guess it's time to get one myself. I do realize that brass has to be trimmed eventually but the hornady
    book says min/max for .308win is 2.005"/2.015" so I was curious if it was necessary since my longest cases still fell under the book max and get close to the same performance from my loads when they were all trimmed at 2.005".
     
    Last edited: Dec 17, 2015
  6. fxdc

    fxdc Da Valley USPSA, SPEED STEEL, IDPA, 3 GUN

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    That trimmer has been the best reloading investment I have made, besides the press.
    LMAO!
     
  7. 2ndtimer

    2ndtimer SE Washington state Active Member

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    Is it safe to load the untrimmed brass? Sure, as long as they are under the maximum length of 2.015". Will the ammo be as accurate as cases trimmed to the same length? Maybe, but probably not. Still begs the question, how accurate is the rifle the ammo will be used in? Is it intended for benchrest competition, or long range target work? Obviously you know what the use will be and your accuracy goals/requirements. I find that I start out only trimming the overlength cases, but usually end up trimming them all back to 2.005". But I am loading for a pretty accurate heavy barrel rifle and am shooting for groups at 100 and 200 yards from the bench, as well as steel out to 1000 yards, so I am trying to get the best accuracy I can.
     
    evltwn likes this.
  8. fxdc

    fxdc Da Valley USPSA, SPEED STEEL, IDPA, 3 GUN

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    Can I ask is this for a bolt gun or semi auto? If for a bolt your FL die are fine if not go to a small base set with a taper crimp die.

    RCBS Black box 308

    It will assure reliable feeding .
     
  9. sprink

    sprink Battle Ground, WA Member

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    Yes, it's a bolt gun.
     
  10. ma96782

    ma96782 Vancouver, WA Well-Known Member

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    IMHO....

    Consistent ammo is one of the first steps to accuracy. Then, every little bit helps.

    So for me, all cases are trimmed to the same length. The primers, powder and bullets are taken from the same lot. The die settings are the same for that batch of re-loads. Get it?

    How much will my accuracy be off, if I don't do it that way?

    Who knows and I don't really care. I have only a limited time to be out on the range.

    ++++++

    Since you mentioned that you're using a bolt gun. I guess this story may be of some interest. It's more about headspace rather than case length but still......think about it.

    STORY:

    My reloaded ammo fit my M1a easily. But, when I tried the same ammo in my bolt action Rem 700....well, it didn't chamber. Humm.....ok, so I screwed down the re-sizing die down a bit more. The new ammo is just passing, in the gauge test. Remember, there is a high and a low cut, to test for re-sized brass to still be acceptable. Now, the ammo would work in both rifles.

    Bottom line: chambers vary and a little bit could be all the difference.

    And.......cam over, while re-sizing. I hope you're doing that...RIGHT?

    Aloha, Mark

    PS....I use a standard F/L sizer die. I've never found a need for a SB sizer die. Measure and trim (if you're gonna be doing it) AFTER sizing.
     
    Last edited: Dec 17, 2015
  11. misterarman

    misterarman Vancouver,Wa. USA Silver Supporter Silver Supporter

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    Don't forget about neck sizing for cases fired from your bolt gun.