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Thread: .22/.17 rimfire DIY rim gauge and results

  1. #1

    .22/.17 rimfire DIY rim gauge and results

    I have always wondered if the anality of measuring rim thickness really does make a difference to consistency.
    As I was bored and clearly had too much time on my hands I thought I would give it a go.

    Rather than drop 60 on two rim gauge it occurred to me that a .243 empty is a perfect comparator for .22WMR and .17HMR rim thickness and a .22 centrefire case would work perfectly for .22lr and .17M2 rim thickness.
    Saddler (Jon) on here was kind enough to give me a couple of .223 empties for the smaller of the two case and I have some .243 already.

    Easy enough to do, measure case in calipers and zero, drop the rimfire round and read off new measurement
    I re-zeroed every 3 rounds and opened and closed calipers a couple of times on each round.

    using fairly small sampled of 40-100-

    First up .22lr subs
    I have a selection of:
    Winchester - measured between 0.97mm and 1.03mm (variance of 0.06mm)
    Eley - Measured between 0.99mm and 1.02mm (variance of 0.03mm)
    RWS - Measured between 0.98 and 1.11mm (variance of 0.13mm! shocking compared to the others and this was the smallest sample of less than 40)

    Next the .17M2 (my favourite of the HV rimfire rounds)
    CCI 17gr
    pretty much a 25:25:25:25 split between 1.03mm:1.04mm:1.05mm:1.06mm with a couple at 1.02mm(variance of 0.05mm)

    Next .22 WMR
    Remington 30gr Gamepoint -
    amazingly they all measured either 1.17mm or 1.18mm (a variance of only 0.01mm!)

    Next up CCI 20gr HMR
    measured between 1.14mm and 1.20mm (a variance of 0.06mm)

    Will test out the .17M2 tomorrow hope it is not too windy!
    I am making the assumption that a batch of sized rounds will group better than a batch of random rounds.
    My plan is to test one batch of sized, one batch of sized but with a range from large to small and one batch of random unknown sizes.

    I am hoping to join an indoor range next week and test the .22lr subs

  2. #2
    Smart idea. More folks should engage their brains instead of their wallets when it comes to shooting gear!~Muir

  3. #3
    ever measured .22 rims? any conclusions?

  4. #4
    Quote Originally Posted by bewsher500 View Post
    ever measured .22 rims? any conclusions?
    I have. Many actually, but as a QC inspection, not necessarily for accuracy. Sorting by rim will effect accuracy. 22-50BR bench rest shooters do, or some of them do, but that is a different discipline from field shooting. In practical use it's ok for target shooting from a gun that maintains a clean chamber and breech (powder residue build up will change headspace) but in the field it won't show much improvement. Most serious shooters stick with a quality ammo that has given consistent accuracy and don't worry about it. Sorting by rim thickness has its greatest value when you have the desire to make a silk purse from a sow's ear and segregate cheapo ammo for greater consistency. You will almost always see an improvement in that instance.~Mir

  5. #5
    How did your testing go?
    I'm wondering if rim thickness sorting might help my HMR consistency. I have found the Winchester ammo quite hard to lower the bolt in my Anschutz probably due to the average rim thickness of 0.047". My batch of Hornady averages 0.044" and has no headspace issues. Both shoot the same.

  6. #6
    Bewsher maybe run the test firings over a chrono whilst checking groups - it would be interesting to see if there was any difference that relates to rim thicness headspace variation.


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