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  #1  
Old 06-19-2009, 06:45 PM
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Ammo tolerances


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I have recently started giving my commercial ammo, .38 Special with an average range of 195gr to 210gr total weight, a quality check before using it in my guns. I check for overall length, gross weight (in grains) and high primers. I haven't really had any problems to prompt this but since I spend so much time checking my guns (I LTI before each range session and then function check thoroughly after cleaning) that it only made sense to start checking the ammo. As I handloaded for years I know what I am looking for. Mostly I want uniformity within a lot, I am looking for functionality here, not accuracy.

Now here is the question: How critical should I be in overall weight? I have noticed weight deviations within a lot in even the best quality ammo of .2-.5 Grains. I have also noticed up to 1.0 grains difference between different lots of same cartridge , is this normal (fluctuation in powder types,brass, bullets etc?)

At what deviation from the Average should I start culling?
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Old 06-19-2009, 07:49 PM
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The only answer I could give you would be -- experiment. Sort them out, shoot comparative groups under as consistent a set of conditions as you can arrange. Tabulate your results and see if you can determine any significant difference. These seem to be, at least at first glance, fairly normal variances you are seeing. Whether or not they mean anything to accuracy is something you just have to find out by shooting.
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Old 06-19-2009, 08:25 PM
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I have discovered that case weight can vary even between lots from the same factory. Apparently the difference is in the web, some are thicker than others. Normally they will fall into two weight groups. That may have to do with the machines. In any case, I have pulled loaded cartridges and found very little difference in powder weight but a bit of variation in case weights.
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Old 06-21-2009, 08:00 AM
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Quote:
Originally Posted by mtmrolla View Post
. . . In any case, I have pulled loaded cartridges and found very little difference in powder weight but a bit of variation in case weights.
I would also give factory bullets, be they jacketed or swaged, a "thumbs up" for consistency in weight.

I wouldn't be too concerned about factory ammuntion weight variations of a half grain or so as mtmrolla said, "a bit of variation in case weights" seems to be common. Many bullet casters are perfectly satisfied with half grain tolerance in their bullets which BTW, shoot just fine.
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  #5  
Old 06-21-2009, 06:32 PM
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The factory case trimming method is not as precise as the handloaders, and you often case length variations due to that, and weight variance comes with it.

If you sort cases by weight, you usually discover several discrete peaks in the weight distribution indicating the cases came off several sets of tools and were mixed in the packaging. The same can happen with bullets, depending on the brand and quality.
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Old 06-21-2009, 07:00 PM
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Beause I'm retired,with time on my hands,I weigh a lot of stuff.
Bullets,except for Sierra,vary quite a bit;cases even more so.
Just sort your loaded ammo in 3 groups;light,medium and heavy.
Now,see if any group is more accurate then the others;or then your origional groups.
Not an easy task.
Frank
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Old 06-24-2009, 05:26 PM
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A few questions.
What is LTI?
What are you checking - match .38 WC from Federal, Winchester or Remington?
Have you noticed a performance issue?
The first question is to further my knowledge of various terms.
The second is related to what you are checking; some of these are very high quality and checking overall weight might not prove anything.
The third is related to why you would spend your time doing this; each to his own. I would not bother unless called shots in the 10 ring were well out. I would rather spend the time reloading more ammunition or practicing.
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  #8  
Old 06-27-2009, 01:59 PM
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From the context I am guessing, "Load Them Individually".
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