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Discussion Starter · #1 ·
I set my trimmer to the desired length, and checked every case and noticed it wasn't the same length every time. The length lock was tight but wonder if I put to much pressure on the shaft on not enough could that be the diff. Im talking only a thousanth +-
 

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Most trimmers will not cut to the same length every time and it has to do with, as you guessed, pressure. You'll get the hang of it eventually but it can be exasperating. At one time someone made what was called a file trim die for case trimming. I'd guess that would work but the rotary trimmers are much handier and will work once you've used it for awhile. The amount of length variation you're talking about probably will not make any difference. Your main objective is not to be OVER max length.
 

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resizing

i have not started reloading yet,but I have over 100 once fired (from my M1a)factory brass and will get a loader soon.Do I need to full length size these? or is neck size going to bee adaquate?
 

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I Realize Some Here will Shudder at this Thought, It only Pertains to me and Mine Only
As already Stated it can be Exasperating there are so many variables when measuring the case , are the calipers square to the case?? Is the Case Head/Rim Straight,Bent Slightly as you cant really see it? You get the Point
I like using Hornady 150 grain FMJBT bullets and to give a little extra neck to help hold them, I set my case trim length to 2.008 and if i am within 3 thousands either way I am happy and Good to Go
And when you process 2100+ 5.56, 800- 30-06 and 1600-7.62 in a week you cant sweat the small things

Now my hunting rounds are a whole other ball game
 

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i have not started reloading yet,but I have over 100 once fired (from my M1a)factory brass and will get a loader soon.Do I need to full length size these? or is neck size going to bee adaquate?
The M14 gas guns brass must be full length resized, if you want them to work flawlessly.
 

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Discussion Starter · #6 ·
So if the trim specs call for a measurement, should I ad a thousanth so it doesnt drop under the called for spec?

if the measure meant is +- a thousanth when you load it will be to does that matter
 

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So if the trim specs call for a measurement, should I ad a thousanth so it doesnt drop under the called for spec?

if the measure meant is +- a thousanth when you load it will be to does that matter
Short answer = YES

Hornady manual cites 2.015" max & trim to length 2.005".

Like Charles, I trim to 2.008" because some cases end up slightly shorter and some slightly longer. Usually only +/- .001. Depending on how much you are trimming off, deburring & chamfering may shorten the case a bit more. My last two batches of cases were once-fired Winchester white box. Length after re-sizing was anywhere from 2.022-2.034". Hand trimming was a PITA!
 

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If you use the RCBS X-dies, the directions say to trim to 1.995. I have had no real problems so far with about 850 of 1000 rounds of virgin IVI trimmed to that length. I have had a couple neck tension problems (bullet unseated), but I'm not sure the trim length is the culprit as these few cases were pulled down and reloaded again, probably stretched out the neck when pulling the projectile. YMMV, so do what you feel is safe. Sticking to reloading manuals will always be the safest route.
Yes trim pressure is the key, I can vary trim length by a few thousandths just by pushing harder, or lighter on the lathe trimmer.
Also, not only MUST you full length resize, you may want to (or rarely need to) use small base dies.
 

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Cases at the max length should be fine in any 308 chamber. It's just based on the SAAMI chamber spec, probably with a margin taken off to ensure it'll still work in the shortest possible chamber.

Trim-to length is arbitrarily set at 0.010" shorter than the max. It doesn't really matter if your 1 or 2 or 5 thousands off of that. Even 0.005" of variance in trim length is going to be hard to measure on any target.
 

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I've owned several of the rotary-style trimmers over the years and they all gave me some variation (except for the L.E. Wilson trimmer which is excellent and not that much more expensive than the rest unless you get every option they make). There are several sources for the variation, but as long as you're not over the max length or seriously short, you're not going to run into any dangerous situations. You may not get the best accuracy in the world if all your cases have a different length, but nothing will blow up unless one is too long, or so short it won't hold the bullet properly (bullet is driven further into the case during cycling in the gun).

The best trimmer I own by far is the Gracey. It takes about 3 seconds to trim, deburr, and chamfer a case - and they're all the same length. The problem is a Gracey runs about $280 plus a shell-holder for each caliber. http://www.matchprep.com/trimmer.htm And it's a real pain to change calibers - a REAL pain. But if you have several hundred cases to trim (or if you scoop up a few thousand on the web) it's hard to imagine doing without it.
 
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