Measuring rimfire ammo

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  • Measuring rimfire ammo

    Well I'm convinced rim thick measuring works but iv found a better way, simply measure the entire length of the bullet. As rim thickness indicates case length and the projectile getting close to the lands, why not measure the whole bullet? A long case could have a more reply seated projectile, a short one might have a less deeply seated round.

    So measure the whole round!

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    I also use a inverted cutlery drainer with the holes drilled out to sort the rounds in length order. Soon I might compare a few that are 25.015 long with some that are 25.020 long and see if there is any point in sorting them in divisions of .001 (or .01 if I'm missreading the micrometer) I might sort them in groups rather than the tiniest differences.

    Click image for larger version

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    It makes a difference! By I think a shorter breach where the shortest round is touching the lands would remove the need for measuring, as would target grade ammo, I think. But it's fun!

  • #2
    Sorry I don't see how the length of a round if relevant. A rimfire round heads laces off the thickness of the rim. What you're doing is like measuring to the tip of a bullet when you should be measuring to the ogive.

    Be interested to hear if you think it makes a difference

    Steve

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      That's a bit I forgot to mention, a few times I measured a round and then tapped the end of it hard on the tabletop a few times, it was hard to see the flattening, if there was any to see. At worst that made little difference to the measured length of it, less than one division on the micrometre.

      The distance from the tip to the ogive iis pretty consistent making the overall length the important bit

      This will catch on!

  • #3
    Hi Chewtah, that's seems feasible I will check some of my rim thicknessed rounds to see if they are consistent in length.
    Have you shot any of the batched rounds yet to see how they go?

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      Yes, I'm conviced they are more predicable due to sorting. I think your thick rimmed ones will be short and the thin rimmed ones long.

  • #4
    Measuring the overall length does not have as much influence as measuring rim thickness and weight sorting., There is too much variation in the projectile manufacturing process. Base to ogive is what you should be measuring and, as you can't really alter this with .22LR there is not much point.

    The best way to sort for accuracy is to weigh each round, and then measure rim thickness. Worked for me when I did benchrest. Below is an example of a 5 shot group shot at 50M (outdoors) with an Annie MSR 64. The ammunition used was weight sorted and rim thickness gauged Lapua X-Act.

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      I see your point as it the ogive meeting the lands but they do shoot when when sorted this way, maybe better again when measured base to ogive. Now if I weigh and measure how do I sort them, heaviest and longest together? I might get a longer one that's lighter in weight? How do I sort that one?

  • #5
    It's a very time consuming process, but what you are actually after is consistency. Weighing and gauging gives you batches of ammo you know are consistent, which is supposed to reduce the chances of a random flyer, which is critical in benchrest.

    What I did was get a sheet of a4 paper and, with a texta, divide it into say 10 squares. Get a pack of ammo, and weigh the first one, sit it in the first square and write the weight down in that square. Now, one at a time, weigh the rest. If the next one is the same weight, place it in the first square. If it is heavier, or lighter place it in another square and write the new weight in that one. Weigh the next one, same as last? Yes, into that square, No, another square.

    So on and so on.

    You should see a pattern start to form, some will be lighter, some will be heavier. It's up to you what sort of tolerance you use, it is also dependant on your scales and measuring equipment. I have a set of digital scales that tell me they can read 0.01Gr, not sure I believe it, but it's the consistency you are after.

    Now do the same thing with the rim thickness.

    Eventually, you should end up with batches of ammo that weigh the same, and have the same rim thickness.

    Below is a picture of the rig I made to measure rim thickness. It's an old bench comparator from work with a hardened and ground bullet holder. Pop the first one in, set zero, and off you go.

    Like I said, it sucks up a lot of time and effort.

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