Commercial ammo tolerances?

Commercial ammo tolerances?

This is a discussion on Commercial ammo tolerances? within the Defensive Ammunition & Ballistics forums, part of the Defensive Carry Discussions category; I have recently started giving my commercial ammo a quality check before using it in my guns. I check for overall length, gross weight (in ...

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Thread: Commercial ammo tolerances?

  1. #1
    Senior Member Array wjh2657's Avatar
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    Commercial ammo tolerances?

    I have recently started giving my commercial ammo 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.

    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?)
    Retired Marine, Retired School Teacher, Independent voter, Goldwater Conservative.


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    VIP Member Array Blackeagle's Avatar
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    What kind of ammo are we talking about? Pistol or rifle? Match, self-defense, or practice ammo? (I would say "cheap practice ammo", but there's no such thing these days) What caliber?

  3. #3
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    A One grain difference isn't much.

    Consider that the brass will not weigh exactly the same, the bullets will not weigh exactly and the primers will not be exactly the same.

    Most manufacturers use a powder tolerance of .2 grains, so it could be a tenth of a grain lighter or a tenth of a grain heavier.

    Considering that all of the tolerances stack up, and considering the manufacturing methods used, its really amazing that they can get the weights of all components as consistent as they do.

    Normally the more powder that is used the higher the tolerance will be. I read that the .50 BMG which uses around 220 grains of powder has a tolerance of 8 grains, 4 up or 4 down,which to me seems really high, but in reality it has little effect.

    Of course, with the pipsqueak rounds that only use 3 or 4 grains, the difference of a half grain is a huge difference that could result in too high a pressure.

    As for being critical, I think the real test should come in how it shoots. If you can hit accurately and consistently, that is what really matters.
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    Senior Member Array wjh2657's Avatar
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    Quote Originally Posted by Blackeagle View Post
    What kind of ammo are we talking about? Pistol or rifle? Match, self-defense, or practice ammo? (I would say "cheap practice ammo", but there's no such thing these days) What caliber?
    My bag! .38 Special Standard Pressure. I will be using both range (WWB, MAGTECH and Federal) and Carry (Hornady & Federal) Bullets will be FMJ 130 gr (practice) and JHP 125gr (carry).
    Retired Marine, Retired School Teacher, Independent voter, Goldwater Conservative.

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    Member Array LouisianaMan's Avatar
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    +1 to HotGuns.

    I have never disassembled and weighed factory ammo, but for the 125g & 130g factory bullets you mention, I'd be thrilled to find that they were all within 1 grain of each other! And then to factor in the brass, powder, and primer. . . .I'd say the variances you're finding of .2 to .5 grains are astoundingly good. Magnificent is a better word. :-)

    Happy shooting!

  6. #6
    Senior Member Array wjh2657's Avatar
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    Being a former Science teacher (physics and chemistry) I am a numbers guy. Since I am setting broad operational parameters, I am accepting 1 SD +SEM(.1 gr for my RCBS Rangemaster 750 scale) as confidence ammo. This is the ammo I use for fast double action work and carry. Ammo at 2 SD +SEM I set aside for slower fire, where I can hear report and see exit of bullet (target strike). This undoubtedly ubercritical and in excess of real performance, but it does give me a feeling of confidence that the ammo I am firing fast is well within the ammo manufacturers specifications.

    So far I have done it with Hornady ammo (carry) and Winchester 130 gr fmj target ammo (WWB). Both have little variation and less than 10% of the ammo falls outside my parameters. The commericial ammo so far has been very consistent.

    A also check for high primers and case and overall length (GO/NO GO Gauge.)
    Retired Marine, Retired School Teacher, Independent voter, Goldwater Conservative.

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