Ball micrometers?

T

TrxR

New member
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
 
TrxR said:
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
Click to expand...

Yes that’s a good mic for measuring neck thickness. For reloading purposes I don’t see a need for the adjustable anvils.
 
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?
 
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.
 
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TrxR said:
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
Click to expand...

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
 
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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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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.
 
liljoe said:
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
Click to expand...

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
 
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
 
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.
 
Al Nyhus said:
...a flat faced, non ratcheting Mitutoyo micrometer is what I use.

Good shootin'. :) -Al
Click to expand...

I believe in having measuring tools in every room on the property so.... I have 2-3 name-brand calipers and some name-brand "reference" mics, also some expensive manual models of each, and literally dozens of others, copycats/knockoffs.

Everyone in the house knows that it's a sin to leave dad's measurers closed...... "use 'em, but put them back like you found 'em"

I found the following to be humourous......

I have a ChiCom digital Micrometer that reads to the "half-billionth" like all the "good" ones and is wikkid good. As repeatable as a gage block, but the ratchet is on backwards! The monkeyboys who pirated the thing were too iggerent to know WHY there's a ratchet so they just "put a ratchet mechanism on there!"

The thing just suuuucks to use. I'm the kinda' guy who, when I put my little tape away I'm halfway acros't the job before it's retracted and when I go to spin this mic back open for the next measure it sounds like the sun going down on cicadas......if I could superglue the ratchet, I would.
 
I use 1/10,000 dial indicator and a Sinclair jig that uses a rod for the anvil.

Give the case a gentle spin and watch the variation all the way around.

It really matters at the edges of the accuracy game sine it c enter the bullet up in the leade if the case is uniform all the way around.

But an off center bullet is going to center up, right?
What could it really matter?
 
I have tubing mics, but.......

.....my runout fixture, with "tenth" indicator, is much more handy.

Kevin
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brickeyee said:
..........................
But an off center bullet is going to center up, right?
...............................What could it really matter?
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How could an off center bullet possibly "center up?" What's the driver, the mechanism for this? To me this is the same as pretending individual bullets in groups "converge with distance cuz they fall asleep"

Matter? I guess this is for you to decide :)



EDITED TO ADD..... I just re-read your post....

Methinks I was hasty.

And misunderstood ye ;)

apologies
 
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