Another Trimming Question


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RJS34
November 14, 2008, 01:07 AM
I try to get my brass all within .0001 in length. Is this necessary? This is for deer and elk hunting so accuracy is very important. I have noticed when I deprime the used brass the case will stretch anywhere from .0001 to .0005. I guess my ultimate question is how important in terms of accuracy is the overall lenth? If I am within .0005 is that good enough or should I shoot for closer?

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The Bushmaster
November 14, 2008, 10:19 AM
.0001?? Don't you mean .001?

.0001 is one ten thousands of an inch (same with .0005). I do have micrometers that will measure that small, but I doubt that is what you are meaning. .001 is one hundredth of an inch and more like what you may be meaning.

Am I right? If so... Then +/-.001 is very possible but not necessary. +/-.002" is more reasonable and much easier to attain.

Walkalong
November 14, 2008, 10:54 AM
Ditto the Bushmaster.

+ or - .001 is more than good enough. Relax and enjoy your hunting.

RJS34
November 14, 2008, 10:58 AM
:rolleyes:

Yeah, that's what I meant. I posted too late last night. Thanks.

USSR
November 14, 2008, 11:13 AM
I have noticed when I deprime the used brass the case will stretch anywhere from .0001 to .0005. I guess my ultimate question is how important in terms of accuracy is the overall lenth?

You are trimming AFTER resizing your brass, correct? For the purpose of hunting at the distances that hunting is normally done, it's not that critical. When I was shooting at 1,000 yards, I found I would sometimes get stringing if I didn't trim my cases occasionally.

Don

SASS#23149
November 14, 2008, 11:45 AM
the main purpose of trimming is to keep the case neck from espanding beyond the walls of the chamber and creating a pressure spike.Most books have at least a .006 variation in oal and' trim to ' length. I doubt that most of us could tell the difference as long as their brass falls within that spec....at hunting distances that is.

1858rem
November 14, 2008, 02:29 PM
do you trim before or after you size the cases?

1858rem
November 14, 2008, 11:32 PM
i tried trimming cases after depriming and sizing, but the trimmer/length gauge(LEE) wouldnt fit all the way into the shell, stopping at the small ledge about a 1/4" away from the blades, i can trim them if i run them through the expander, but only with slight pressure, cause if i put a descant bell on them it wont trim, and if i try to trim without sizing but deprimed it wont trim, so when do you measure the overall CASE length and at what stage should you trim the cases?

SlamFire1
November 14, 2008, 11:53 PM
Trimming is a safety measure. You trim after sizing the case.

As for length, to me it seems if length was critical for accuracy, then it would be the distance from the shoulder to the case mouth. Not the distance from the base to the case mouth. Because in a rimless cartridge, the shoulder is the stopping point.

I have a Gracey and a Giruard trimmer. Trim length is based on where the shoulder touches the shell holder. Not the base. And yet, I easily notice .002" differences, as measured from the base, from shells fired in the same rifle, and sized in the same die.

So I think base measurements are not that exact.

The most critical things for accuracy, in my opinion, are good barrels, good bullets, and good bedding. Trim length in is the noise.

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