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Ballistic Accuracy Classification

Ben from Bison Armory on firearms accuracy emails this.

As he says, a quick and easy way to talk about rifle accuracy that is statistically accurate and meaningful in everyday parlance.

5 Responses to “Ballistic Accuracy Classification”

  1. Joe Huffman Says:

    Nice. I’m not sure it’s all the easy for “everyday people” to discuss the computation of multi-dimensional probability density functions but the spreadsheet turns that into “magic” and returns a number that is useful.

    This is nitpicking but

    There are two atmospheric effects that can finally create excess variance in one axis: Variable wind will increase horizontal variance.

    doesn’t tell the entire story. Velocity variations also affect horizontal dispersion. It’s a small component but it becomes noticeable at longer ranges and constant winds.

  2. ben Says:

    Right, but now I don’t have to answer the statistically meaningless question “can your rifle barrels shoot 1″ groups?” anymore. Now I can say that our barrels are typically class X. Still working to determine what X is. Taking a lot of range trips to gather the requisite data. How I suffer for the shooting public 🙂

    As fit the influence of velocity variance on horizontal dispersion… How far are these long ranges? Are the influences big enough to be measured or do they end up in the noise? A lot of theoretically interesting influences on rifle accuracy that I’ve looked into end up being unobservable in practice. Like called fliers, you never really know for certain as there’s no truth data for comparison, so all you are left with is the statistics, for which meaningful group sizes are required, and beyond that, the investigation would need difficult to achieve controls.

  3. Lyle Says:

    BAC also means Bindon Aiming Concept. A bit off topic, but it still applies to rifle shooting.

  4. Joe Huffman Says:


    Details are here. The bottom line is that is something on the order of 5% to 15%, compared to the effect of the wind itself, at 500 to 1000 yards. It is, of course, dependent upon the muzzle velocity variation, number of shots taken, the BC of the bullet, etc. Not exactly noise, but not major either.

  5. ben Says:

    Awesome Joe, I think you definitively showed that if your rifle is 1/2 MOA then it really matters. Greater than an MOA and it’s getting in the noise. Between 1/2 MOA and 1 MOA, it’s going to be there but hard to see in practice. Thanks for running the numbers!