• alcoholicorn@lemmy.ml
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    7 months ago

    556 was the measure of the inner diameter of the rifling of a barrel of a gun that shot 556.

    Metric is confusing. That’s why for most shotguns, we measure the width by the number of lead spheres of that diameter that would equal one lb, eg a 12 gauge shotgun is the diameter of a 1/12lb sphere of lead.

    Nobody knows how big 18.53 mm is, but everyone knows what a 12 gauge shell looks like.

    Oh, and gun powder is measured in grains, maybe early smokeless pellets were about the same size as grains of wheat.

    • Everythingispenguins@lemmy.world
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      7 months ago

      Grains as a measure of weight comes from the Troy weight system, think Troy ounce of gold. It is a very old system that for a long time was mostly used by apothecaries and probably has its origins in Ancient Rome.

      • bluewing@lemm.ee
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        7 months ago

        Grains Apothecary is used to measure powder charge weight is because it was a “fine” enough scale for measuring small amounts of things that if you get it even a tiny bit wrong, can kill you. So, ammunition manufacturer’s looked around and scales used for accurately measuring small amounts of drugs were commonly available, so they went with that.

        Cool side point: Powder charges are checked by weight and dosed out, (or thrown), by volume as it has always been done since the first gonnes were a thing.