Measuring neck thickness

[Straightshooter1]

View attachment 1360867That picture is a bit of a stretch compared to a real case.

Well, yes. . . the picture exaggerates the amount of difference, but that's the idea to best convey what's going on.

The other issue with neck thickness other than what's illustrated in the picture, is how that difference often can change as you move down from the mouth of the neck to the shoulder junction. Those who've skimmed necks know what that looks like; something like this:

 

[mikecr]

Oh yeah, If you measure at mid-neck, and then measure closer to neck-shoulder junction, you'll see taper in thickness. It's important (to me) to do so, as taper rate can vary as well (which goes all the way to web).

 

[archerforkids]

I feel like I opened a pandoras box. Of course, every time I go to checkout at one of our vendors, I swear this should be all I finally need. Uh huh......cheaper than a booby bar I guess. And my bride is less apt to make me sleep on the couch.

 

[archerforkids]

Thanks for all the input folks. Very informative thread. Like drinking water from a fire hose.

 

[Lone Hunter]

I feel like I opened a pandoras box. Of course, every time I go to checkout at one of our vendors, I swear this should be all I finally need. Uh huh......cheaper than a booby bar I guess. And my bride is less apt to make me sleep on the couch.

The couch isn’t that bad . At least you know where you’ll be and what to expect. Kinda like it there myself… A lot quieter…

 

[archerforkids]

The couch isn’t that bad . At least you know where you’ll be and what to expect. Kinda like it there myself… A lot quieter…

Funny, when I was younger I would get pissed over the couch. Now I don't give a rip, except I can't walk the next day. I think I will stay in graces with her.

 

[Uncle Ed]

the picture on the right is common...even with the best of brass...wouldnt a pressure ring form at the weakest point first? The thin side...sure seems to me it would. I will stay with my ball mics...multiplying by 2 and adding the bullet diameter isnt that difficult.

The problem is if the body of the case also has a thicker side the case can warp when fired. Also, the base of the case can be tilted due to uneven expansion on the thinner side.

Tech Line & Tips (FAQs)​

Concentricity Problems​

a.k.a Neck Runout With Bottleneck Cases

https://www.redding-reloading.com/tech-line-a-tips-faqs/146-concentricity-problems

An interesting experiment also revealed that neck turning of brass that was intentionally sorted as non-uniform, showed little or no concentricity improvement when used in standard S.A.A.M.I. spec chambers. Conversely brass that was sorted and selected for uniformity remained uniform and concentric with or without a neck turning operation.

 

[BoydAllen]

...which is why I wish someone would start making these again. Check out the documents.

SOLD - Creighton Audette case inspection gage

Just purchased this from a fellow forum member and upon arrival realized it will not work for my needs. The mandrel is .250” in diameter and will not work with 6mm cases. That is the only reason I’m selling it and I’m asking what I paid (shipping costs at my expense). $100 shipped

forum.accurateshooter.com

 

[Firearmsunlimited]

So... as I jump down this rabbit hole of turning necks, a question arises. Is it important to actually know the neck thickness of our brass, or know what the variance is we see when measuring different points around the neck? What brings this thought to mind, can we establish variation with conventional micrometer or does it have to be a ball micrometer? My knee jerk reaction is as long as we can establish variation, we can obtain out goal. Obviously the accuracy obtained with a regular micrometer is at play here, but is it any easier or more difficult than with a ball micrometer?
Any help is appreciated.

Why have you decided to start turning your case necks? Do you have a tight neck chamber? What caliber are you working with?

 

[archerforkids]

Why have you decided to start turning your case necks? Do you have a tight neck chamber? What caliber are you working with?

Well....I have been seeing just enough fluctuation in velocity to make me wonder if this might help a little. And no, I'm not running a tight neck chamber.

 

[KMart]

Funny, when I was younger I would get pissed over the couch. Now I don't give a rip, except I can't walk the next day. I think I will stay in graces with her.

Get a recliner. You can thank yourself later.

 

[Firearmsunlimited]

Well....I have been seeing just enough fluctuation in velocity to make me wonder if this might help a little. And no, I'm not running a tight neck chamber.

Variation in neck wall thickness may effect accuracy but not extreme spread. Neck tension, among other things, can effect velocity. If you are shooting a standard SAAMI chamber and you are doing anything other than cutting off the high spots to uniform thickness the best you can you will be creating other problems. Try buying some better brass depending on what caliber you are working with.

 

[archerforkids]

Variation in neck wall thickness may effect accuracy but not extreme spread. Neck tension, among other things, can effect velocity. If you are shooting a standard SAAMI chamber and you are doing anything other than cutting off the high spots to uniform thickness the best you can you will be creating other problems. Try buying some better brass depending on what caliber you are working with.

It was my intention to only skim the necks for starters. This is Lapua brass.
.

 

[mikecr]

Brass brand or price doesn't matter or change what you should do.
You should measure a good bit of it before deciding the best next move.

In this regard,, what we're talking about here, I have seen the best lot of brass and the very worst lot of brass, both in Lapua 6BR cases.

 

[DJSBRS]

A ball mic is a prerequisite to measure correctly and consistently. In addition, knowing how and where and then measuring consistently will provide the necessary results.
DJ
DJ's Brass Service

 

[JMayo]

It was my intention to only skim the necks for starters. This is Lapua brass.
.

I'm gonna play with this also. What i plan on doing is finding the thinnest neck in the bunch and set the cutter at that, then proceed.
First I'll clean them (used brass), size them on a mandrel. Then start my search for thinnest spot.
I'm gonna use calipers.

Just gonna skim the high spots.
Then I'll have to decide what bushing to use now that they are thinner.

 

[barefooter56]

So... as I jump down this rabbit hole of turning necks, a question arises. Is it important to actually know the neck thickness of our brass, or know what the variance is we see when measuring different points around the neck? What brings this thought to mind, can we establish variation with conventional micrometer or does it have to be a ball micrometer? My knee jerk reaction is as long as we can establish variation, we can obtain out goal. Obviously the accuracy obtained with a regular micrometer is at play here, but is it any easier or more difficult than with a ball micrometer?
Any help is appreciated.

A BALL END MICROMETER is the best way to go here.