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Thread: Ball micrometers?

  1. #1
    Join Date
    Mar 2009
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    Ball micrometers?

    Thinking about picking up a Mitutoyo 0-1" 115-313 ball mic to measure neck thickness on my 30br brass.

    Would this be a good mic? Or should i go with something else where the ball mandrel height is adjustable ?

    I can get the mitutoyo or the Sinclair/starrett setup for approx the same price. The mitutoyo is actually a little cheaper due to being in Canada instead of shipping from the us and the currency exchange.

    Thanks

  2. #2
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    why?

    I bought one, used it once.

    once.

    I make a LOT of cases. I'll never use it again

  3. #3
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    Quote Originally Posted by TrxR View Post
    Thinking about picking up a Mitutoyo 0-1" 115-313 ball mic to measure neck thickness on my 30br brass.

    Would this be a good mic? Or should i go with something else where the ball mandrel height is adjustable ?

    I can get the mitutoyo or the Sinclair/starrett setup for approx the same price. The mitutoyo is actually a little cheaper due to being in Canada instead of shipping from the us and the currency exchange.

    Thanks
    Yes that’s a good mic for measuring neck thickness. For reloading purposes I don’t see a need for the adjustable anvils.

  4. #4
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    That Mitutoyo will work just fine.

  5. #5
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    Dec 2003
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    washington.........STATE that is.
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    OK, so would someone please explain to me how and where a ball mic saves time or adds accuracy?

    I lied some when I said "I used mine once"...... I used it once, for a few days.

    I actually measured quite a few things in the week I used it.

    Here's what I did.

    I laid out some neck-turning equipment.

    I laid out some cases.

    I laid out some bullets.

    I laid out some notepaper pads.

    I mic'd a bunch of the bullets, 2-3 places, set them in rows..... hmmm. I wrote down the numbers.

    I turned some necks, I used the new ball mic and I mic'd the necks with the ball mic and wrote down the numbers.

    I added up all the numbers, sevaral times cuz I'm a construction guy, and found that hmmmm.... it looks like I'll have to adjust again.

    And again.

    "OK, the numbers all add up"......"loaded round should measure around .2595"......

    I trimmed.

    I chamfered with the long taper tool and deburred and etc and etc.....

    I picked a neck bushing based on this SWAG and sized a neck and seated a bullet.....

    And then I mic'd the neck with the bullet in it... in about 3 places..... hmmmmm, my numbers are reasonably close but,

    "WHY didn't I just do this in the first place?"

    Some of my turning mandrels are large enough that I can insert/remove a bullet by hand.

    Some I have to pull.

    Some I have to pop out with a hammer tool.

    BUT IN ALL CASES, I find that to be safe, I'll end up measuring over the loaded rounds.

    And in all cases, if I just seat a bullet, measure it and subtract how much I want for clearance.... and spin out some cases......and measure a few dummy rds....which I'm going to do anyway! I never trust my own math. Not when my eyes depend on it.

    bullets vary
    pressure rings vary
    bullet compression varies
    chamfers vary
    bushes vary
    different bushings yield different results

    etc etc

    I mean, all I play with is final clearances..... why do I even CARE how thick the necks are?

    Again I ask..... "why?"

    Fuh'GEDDAbout "is this a good one or not?"....... "WHY?"

    IMO folks come on this board for information.... information which hopefully aids them in making good choices re spending their budget......and it's hoovis of me to pass on information on items I spent my budget on. Would someone please explain to me how owning a ball mic is worth money as an aid to a beginning shooter?

  6. #6
    Join Date
    Feb 2019
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    280
    I use my ball mike often.

    ‘Nuff said

  7. #7
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    Sep 2014
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    88
    "Ball" mic or "Pin" mic?

  8. #8
    Join Date
    Apr 2017
    Location
    DFW, TX
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    Try this procedure

    While I have a ball mic, I find the following procedure using a standard anvil-style digital mic or digital blade calipers is more accurate and repeatable.

    1) Zero the mic or calipers using your intended bullet.

    2) Measure the loaded neck diameter.

    3) Take that number and divide by 2. That's your neck thickness.

    Consistently measuring an "absolute" is hard, especially if you're measuring to the ten thousandths. By using the mic or caliper as a comparator, you can get a more consistent read on the effective neck wall thickness. Many bullet makers (BIB for instance) publish bullet diameter data. If not, for a 6mm bullet, I use 0.2431" as a default value.

    HTH. Good luck.
    Last edited by Kyle Schultz; 09-10-2019 at 11:30 AM.

  9. #9
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    I've always used a Mitutoyo ball mic. Top of the line in my opinion.

  10. #10
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    Lower Dakota Territory
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    Quote Originally Posted by TrxR View Post
    Thinking about picking up a Mitutoyo 0-1" 115-313 ball mic to measure neck thickness on my 30br brass. Would this be a good mic? Or should i go with something else where the ball mandrel height is adjustable ? Thanks
    I have quite a few Mitutoyos, including that one...good stuff. No need for the adjustable mandrel, IMO. The usefulness of a ball micrometer depends on the individual person.

    Good shooting. -Al
    Last edited by Al Nyhus; 09-10-2019 at 01:35 PM.

  11. #11
    Join Date
    Feb 2003
    Location
    Mt Pleasant Michigan
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    This one works well for measuring the thickness of the neck.
    Turn your neck on one case and check with the ball mic, then seat the largest diameter bullet you will be shooting and measure that diameter with a GOOD micrometer and check the loaded round diameter. This is the number that really matters.
    Joe Hynes
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  12. #12
    Join Date
    Jun 2012
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    West central NH
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    I like my ball micrometer just fine, but does anyone use a Sinclair case neck sorting tool? It's pricey, but using a mandrel and a dial indicator, it seems like it would be faster to use.

  13. #13
    Join Date
    Feb 2003
    Location
    Melbourne, AUSTRALIA
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    76
    Quote Originally Posted by liljoe View Post
    This one works well for measuring the thickness of the neck.
    Turn your neck on one case and check with the ball mic, then seat the largest diameter bullet you will be shooting and measure that diameter with a GOOD micrometer and check the loaded round diameter. This is the number that really matters.
    Joe Hynes
    I use the one pictured only difference mine has a chamfer on the stem to get close to the neck/shoulder junction. Back around 20yrs ago Russ Hayden or Ron Hoehn used to sell them with the chamfer.

    But also the more experienced you are at neck turning, the more what Al says is true. You could just use a plain micrometer. Measure along neck and work out what clearance you want to run for the type of bullets you are using.

    I run on the conservative side as I don’t want issues changing from a BT to FB bullet

  14. #14
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    I will add that for the final measurement of a neck with a bullet seated...a flat faced, non ratcheting Mitutoyo micrometer is what I use.

    Good shootin'. -Al

  15. #15
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    Kentucky-Home of the Kentucky Wildcats
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    The only dimension that matters is the loaded round diameter. Measuring in tenths consistently is a prime example of an area for tolerance(measuring) stacking issues and I've just never understood why people feel like they have to measure by brass thickness when all that matters is the loaded od...and is much easier to reliably measure. Just my 2 cents and both ways can work but just seems like taking the hardest way to go about it.

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