case trim length

Discussion in 'Reloading' started by TBuckus, Jun 27, 2013.

  1. TBuckus

    TBuckus Well-Known Member

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    In my Lyman book, it states the case length for the cartridge. Many state trimming .010 under the case length.
    Is that .010 under the case length, or is the case length what I am supposed to trim to?
     
  2. jimbires

    jimbires Well-Known Member

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    case length would be max length , trim your brass .010 shorter . this will work for you . I think my old books had case length , and trim to length .

    sinclair sells a case length gauge that will allow you to measure exactly how long your chamber is cut ,then you can use that measurement as max case length , if you're interested .
     

  3. AZShooter

    AZShooter Well-Known Member

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    I used to trim cases often till I read what Varmint Al had to say. I suggest you read his comments and decide what you would like to do:

    Varmint Al's Handloading/Reloading Page

    I made my own chamber length plugs based on his supplied dimensions but you can buy them, as the last poster stated, from Sinclair.

    Sinclair Chamber Length Gage | Sinclair Intl

    I now have measurements for every rifle's chamber length. I like to keep the brass .010" shorter than that dimension.

    Factory chambers are usually very long. Some of the brass will never require trimming. If the case got to the end of one of those chambers you would have a case head separation before you needed to trim. I have seen a few chambers that were over .070" longer than new brass!
     
  4. Mikecr

    Mikecr Well-Known Member

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    As far as I know, 10thou under chamber end works well and is conservative enough provided it's watched. And you'll probably manage to get this close only with an aftermarket barrel/chamber anyway, as a factory won't let you get so close.

    Where I have a choice I set 5thou under chamber, to reduce ES.
    I can get away with it because I never FL size, and my headspace is managed so my case lengths don't change with reloading cycles.
     
  5. TBuckus

    TBuckus Well-Known Member

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    I like the homemade trim length gauge mentioned. My guess is that I don't need to trim my new brass. I'll have to play around with finding out my chamber length.
    Thanks for the advise.
     
  6. TBuckus

    TBuckus Well-Known Member

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    Thanks for the info. I made a home made gauge and found out that I can go out to 2.125 on my Tikka. (2.100 and 2.090 for book references for a 300wsm)

    Now i'm not concerned about trimming as much as I was.
     
  7. Gene

    Gene Well-Known Member

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    I have been trimming my .223 to .005" under SAMMI before FL sizing. Then I discovered they were growing about .006-.007 after FL sizing, making them too long. Best to trim after sizing.
     
  8. Mikecr

    Mikecr Well-Known Member

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    TBuckus, it won't hurt anything if you've trimmed them in error. It's just a lesson learned, and if you FL size it won't be long before you get another trim at it anyway. Watch it

    -SAAMI, & book values, don't matter
    -FL sizing causes growth in trim length, it's the only action that does
     
    Last edited: Jul 1, 2013