Micrometer for neck turning

[Lkwebb]

I bought a mitutoyo micrometer for measure the od of my cases that I'm turning. I turned bout 20 cases last year to get ready fire form them.
My chamber is a .269 and my loaded rounds are .267.
Now I had received 9 pieces of brass from a gentlemen who reamed my barrel for me and is also a avid competitor.
Now I measured the o.d of the brass he turned and I tried to get as close as I could to his numbers. Even though i did that my loaded rounds are still .267 instead of .266.
I used the smallest bushing that I had when I fl sized the cases which was the .264.
Now do I buy a ball micrometer to get the right dimensions of the turned case or buy a .263, .262 bushing so my loaded round would .266

 

[CNC-Dude]

A ball mic probably wont help you because it is too big to fit inside the case necks. You need a pin mic to do what you are wanting to do. Also, if we get caught using digital mics or calipers to measure production parts at work, we get 3 days off without pay....

 

[6bra1k]

no,,,you need to measure a seated bullet, not just the case.
measure a bullet at the base/pressure ring.
seat the bullet with the base pressure ring down 1/2 the length of the neck.
measure the neck at the middle ( ,0001 mic)
do the math ( seated dia minus bullet dia, divide by 2 equals neck thickness)

 

[209jones]

Gage pins would help you with measuring the ID, they're cheap. Lots of articles around on those to help you decide what to buy there, the come in plus or minus sizes, may want both for your purposes. Check to see if your bushing really is 264 or not, get a 263 if you need to. Neck hardness can affect springback if not annealed.

 

[Lkwebb]

Gage pins would help you with measuring the ID, they're cheap. Lots of articles around on those to help you decide what to buy there, the come in plus or minus sizes, may want both for your purposes. Check to see if your bushing really is 264 or not, get a 263 if you need to. Neck hardness can affect springback if not annealed.

Yes it's a. 264 bushing, the brass is brand new 220 lapua brass

 

[Lkwebb]

no,,,you need to measure a seated bullet, not just the case.
measure a bullet at the base/pressure ring.
seat the bullet with the base pressure ring down 1/2 the length of the neck.
measure the neck at the middle ( ,0001 mic)
do the math ( seated dia minus bullet dia, divide by 2 equals neck thickness)

I have measure it with a loaded round it is .267, I need a .266...
So I either neck turn more or smaller bushing...right ?

 

[209jones]

And if you turn the neck more, you'll need a smaller bushing to get to the neck tension ID you want.

 

[Lkwebb]

And if you turn the neck more, you'll need a smaller bushing to get to the neck tension ID you want.

Okay..
I'm still in my infancy stage of learning the neck turning for a competition barrel etc..
Just don't want to lose a bunch of high dollar brass due to my lack of knowledge..

 

[STRSRLVR]

This is what I use for measuring neck wall thickness along with their holder and it gives very repeatable results.

Mitutoyo Wall Thickness Micrometer with 60 Degree Modification

The Mitutoyo Wall Thickness Micrometer measures wall thickness of tubes, cartridges & cylinders. Our 60 degree modification allows you to take better measurements.

kmshooting.com

 

[Ray123]

Buy a Mitutyo Uni Mike...you can use a piece of drill rod or Dowell pin ...of a size that fit into the case mouth easily as the bottom anvil to accurately measure your wall thickness. Hint retired machinist and its what I use to check, out wall of roundness, wall taper, and wall thickness.

 

[358WCF]

A ball mic probably wont help you because it is too big to fit inside the case necks. You need a pin mic to do what you are wanting to do. Also, if we get caught using digital mics or calipers to measure production parts at work, we get 3 days off without pay....

This is the one I've been using.

https://www.mscdirect.com/product/details/06233092?rItem=06233092

 

[CNC-Dude]

This is the one I've been using.

https://www.mscdirect.com/product/details/06233092?rItem=06233092

That's a good one!

 

[Lkwebb]

That's a good one!

Awesome thanks

 

[358WCF]

I bought a mitutoyo micrometer for measure the od of my cases that I'm turning. I turned bout 20 cases last year to get ready fire form them.
My chamber is a .269 and my loaded rounds are .267.
Now I had received 9 pieces of brass from a gentlemen who reamed my barrel for me and is also a avid competitor.
Now I measured the o.d of the brass he turned and I tried to get as close as I could to his numbers. Even though i did that my loaded rounds are still .267 instead of .266.
I used the smallest bushing that I had when I fl sized the cases which was the .264.
Now do I buy a ball micrometer to get the right dimensions of the turned case or buy a .263, .262 bushing so my loaded round would .266

If I'm reading this right, it seems like the OP is trying to make the OD of a loaded round smaller with bushings? Ain't gonna happen. Yes, a tubing mic is a really good tool to have for neck turning.

I'm thinking that .267" is plenty safe for a .269" chamber, but if OP wants the .266" measurement the brass needs recut .0005" per side. Now, do the math. Let's say it's a .2433" bullet subtracted from a .266" OD case neck=.0227 divided by 2=.01135" or .0114" per side rounded up which will theoretically give .2661" OD on the 1st try if the stars align just right.

There is no mention of cutter pilot or expander mandrel size unless there was a previous post that explained this. Is this where where the confusion lies? The expander mandrel I use for turning 6mm is .243" which will have new brass springing back to approx .242" ID or so. The turning pilot is .242". Lube & a snug fit is needed on the pilot.

Only after necks are turned to a satisfactory thickness, is when bushing size comes into play.

 

[6bra1k]

I have measure it with a loaded round it is .267, I need a .266...
So I either neck turn more or smaller bushing...right ?

NOT IN MY BOOK...not a bushing issue, a neck thickness issue...
and you are showing only three places(.267/.266) which to me means you need a better mic.
neck dia should be measured to 0.0000 min

 

[DngBat7]

This is what I use for measuring neck wall thickness along with their holder and it gives very repeatable results.

Mitutoyo Wall Thickness Micrometer with 60 Degree Modification

The Mitutoyo Wall Thickness Micrometer measures wall thickness of tubes, cartridges & cylinders. Our 60 degree modification allows you to take better measurements.

kmshooting.com

This micrometer was such a great investment. I don’t see a more accurate way.

 

[6bra1k]

This micrometer was such a great investment. I don’t see a more accurate way.

you do not load empty cases in your rifle, you load assembled ammo. that has a bullet seated in the neck of the case. that is the only number that matters. what is the actual dia of a loaded round, how much clearance do i have.
he has a great mic, but he is only reporting 3 places and in neck turning you use 4

 

[hogpatrol]

0-1" Tube Micrometer 0.0001" Graduation Carbide Tipped Neck Ball Spherical Anvil | eBay

Graduation.0001". Accuracy.00024"/0.006mm. Item#: 3496.

www.ebay.com

 

[DngBat7]

you do not load empty cases in your rifle, you load assembled ammo. that has a bullet seated in the neck of the case. that is the only number that matters. what is the actual dia of a loaded round, how much clearance do i have.
he has a great mic, but he is only reporting 3 places and in neck turning you use 4

My mistake. I did not see the initial post. Only the one I commented on.

 

[6MMsteve]

This is the one I've been using.

https://www.mscdirect.com/product/details/06233092?rItem=06233092

when I first started nk turning that Mic was 54.00, think I got it at Sinclair's