Tolerances...

Discussion in 'The Ammo & Reloading Forum' started by .308 shooter, Aug 24, 2008.

  1. .308 shooter

    .308 shooter New Member

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    I've just finished my priming my first batch. Now I have to charge them and load them. I've already adusted my powder dispenser and seating die.

    Prior to this I was measuring the case length and they were all coming up as 2.015. So.... in typical style I "assumed I was good. Now..... I just happened to remeasure them...... everyone this time and found quite a few differences. Some were quite a ways off, I've set them asside. Some were only .001 - .003 off. I know for ideal control, they should all be 2.015, but in an effort to avoid having to do it all over, is that an acceptable tolerance?

    Lessoned learned...... but is it okay to finish the loading process?
  2. Haligan

    Haligan Well-Known Member

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    Yes, you do have ranges of acceptable tolorances.

    Their are so many variables that will account for small differences. I found different brass manufactures to be huge.

    The quality of the projectiles. ex; bulk, match, lead nose(smushes easier.)

    You'll develop a quality control on your own, I can't give you my numbers on what is exceptable because it changes based on the factors listed above.

    You'll look at em' and after a while you'll know. I know one guy from Kalifornia will have a pretty good explanation on this so be patient and he'll be along.
  3. 312shooter

    312shooter Active Member

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    The Lyman manual shows 2.015 as max length, I like to trim at this point to 2.005 for uniformity. Have you read any manuals yet???? Most manuals would clarify this.
  4. .308 shooter

    .308 shooter New Member

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    I did read the manuals.... actually read both the Hornady and the Speers manual, but I don't remember anything about max case length. I saw where it listed the case length, and the COL, but it also said each gun was different and it lists the average COL or tested COL, but that was the measurement for most factory loads to fit most any gun.
    I had some cases which were 2.021 instead of 2.015 and those are definitely being reworked, but only .003 of a difference?

    I would guess that's an acceptable difference, but wanted to get other opinions.

    Thanks.
  5. Bindernut

    Bindernut Well-Known Member

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    .308,

    Both Hornady and Speer manuals have the maximum and "trim-to" length figures in their data. All pertinent specs for a case are listed at the beginning of each section (by the dimensional drawing). The C.O.L for each particular bullet will be listed by each bullet's chart.

    Those cases that are over the max of 2.015" you will definitely want to trim! That is the maximum safe case length...anything longer than that and the case will most likely extend past the end of the chamber into the leade of the rifling....this will cause dangerous high pressures, might ruin a good rifle, and worse yet do yourself some serious harm from the shrapnel.

    Even when using brand new brass, you'll want to full-length resize them before reloading. Measure the brass for max length AFTER they're resized and trim as necessary to the "trim-to-length" dimension listed for your cartridge. General rule of thumb is the trim-to spec will be 0.010" shorter than the max length.
  6. .308 shooter

    .308 shooter New Member

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    Well..... Looks like the Jury is in. I've loaded only the good shells and am in the process of depriming the oversized shells. Case trimmer has been ordered and is due to arrive on Wednesday/Thursday. Just in time to trim and reload for the weekend. :)
  7. LDBennett

    LDBennett Well-Known Member

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    308shooter:

    What the others said!

    The process is you take new brass, size it, and reload it. After the first shooting you clean the brass, size it, then measure it for the COL. The manuals give both a MAX COL and a "trim to" COL. If the cases, any cases in the lot, exceed the MAX COL then trim the lot. You trim it to the "trim to" COL. The difference is typically 0.010 inches. So once trimmed then shot, any length from the "trim to" COL to the MAX COL is acceptable to reload without trimming again. You usually get two to three reloads after trimming before you have to trim again but it all depends on the brass you bought, and the design of the case. Some calibers require trimming for every reload and some go for five or more.

    If trimming is a problem then RCBS makes an X-Die that requires one trimming and then the brass never need to be trimmed again and the life of the brass tends to get extended up to 12 or more reloads (without trimming), it says here (??). I'm testing this approach on my 308 ammo for my FAL but it may be years before I get to 12 reloads of the brass! I like the concept of 12 reloads before the brass dies instead of four or five (if that many). Not having to trim is nice but extending the brass case life is what entices me. But I'll not recommend this to anyone until I see it myself. Stay tuned...but it may be awhile!

    LDBennett
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