Parallel Neck Rims

[Koda]

What would cause the rim of the neck to not be square, or more precisely, parallel to the base? Is this an issue to fix?


Photo isnt the greatest as I tried to get the light to show the gap. This is twice fired Nosler Premium brass and fully sized, I dont need to trim it but have been to square them up but it keeps coming back.

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[Member 34319]

Metal bends to pressure. Take 60,000 psi to something and see if it doesn't move a bit.

 

[Koda]

Metal bends to pressure. Take 60,000 psi to something and see if it doesn't move a bit.

True. Although I'm really surprised how little these cases grow from fireforming. This is my first time reloading an Ackley Improved case and Im impressed with how little it grows. I don't even have to bump the shoulder back when sizing, it just doesn't grow.
But I noticed the uneven rim right away. I trimmed the case down to even them out. Fired them and they grew a couple thou but unevenly. My guess is the brass thickness is uneven but I dont have a way to measure that.

 

[DizzyJ]

Differences in thickness around the case can cause it to stretch unevenly resulting in a slight "banana" shape.

I suppose a bolt face that's out of square could cause something like that as well.

 

[Koda]

Differences in thickness around the case can cause it to stretch unevenly resulting in a slight "banana" shape.

I suppose a bolt face that's out of square could cause something like that as well.

I dont think its the bolt face, rifles brand new and a good one Id be ticked to find an issue with it and have to send it back. Im already dealing with a warranty on a brand new unfired gun at the moment too... (still ticked about that)

Anyways, so I checked my brass supply and the issue is there. Brand new virgin unfired Nosler "premium" brass looks just like my pic. I dont have a way to check/measure wall thickness but thats my guess. Im guessing this might affect my accuracy now...

 

[DizzyJ]

I dont think its the bolt face, rifles brand new and a good one Id be ticked to find an issue with it and have to send it back. Im already dealing with a warranty on a brand new unfired gun at the moment too... (still ticked about that)

Anyways, so I checked my brass supply and the issue is there. Brand new virgin unfired Nosler "premium" brass looks just like my pic. I dont have a way to check/measure wall thickness but thats my guess. Im guessing this might affect my accuracy now...

It may or may not affect it. If so, to what degree?

 

[Koda]

It may or may not affect it. If so, to what degree?

wouldn't inconsistent wall thickness at the neck affect group size?

Im in the middle of load dev, ran a few pressure ladders and next I will find out soon enough next range session Im shooting for groups.

 

[DizzyJ]

wouldn't inconsistent wall thickness at the neck affect group size?

Im in the middle of load dev, ran a few pressure ladders and next I will find out soon enough next range session Im shooting for groups.

It certainly could.
Depends on how extreme the variance is.

 

[Koda]

It certainly could.
Depends on how extreme the variance is.

I dont have a way of measureing this. Is this where one of those concentricity gauges come in?

 

[DizzyJ]

Dial indicator and mandrel set up on a stand will show case run out and or thickness variations.

A ball micrometer will also show this.

 

[bionic knees]

trim some back to square, load and shoot and recheck. if they come back out of square then start looking.

 

[Koda]

Dial indicator and mandrel set up on a stand will show case run out and or thickness variations.

A ball micrometer will also show this.

I actually have a dial indicator, but just the indicator. Nothing to mount it on.
Not really wanting to buy more inspection tools... I think I should look for new brass.
Except right now Nosler is the only company putting out new brass, that I can find anyways.

 

[Koda]

trim some back to square, load and shoot and recheck. if they come back out of square then start looking.

Done it. They come back out of square. I should look for new brass I think but I have to work with what I got for now...

 

[Provincial]

Set up a rod slightly smaller than the inside diameter of the case in a fixture (block of wood, vise, etc.) that holds it extended far enough to support the whole neck of the case. Vertical would probably be the best for accuracy. Stick the mouth of case on the rod. Set up your dial indicator so it reads the thickness of the neck (zero it on the rod with no case and it will read the neck thickness. Holding the neck in full contact with the rod while under the tip of the indicator, rotate the case to check variation. You should be able to check quite a few necks in a short amount of time.

Mark the thinnest point on the neck of each case. See if there is a link between the thin point and the runout of the mouth (parallelism), and trim a couple of cases square to use to test if the neck flows at the thin point when fired. These tests should tell you all you need to know.

 

[Koda]

Set up a rod slightly smaller than the inside diameter of the case in a fixture (block of wood, vise, etc.) that holds it extended far enough to support the whole neck of the case. Vertical would probably be the best for accuracy. Stick the mouth of case on the rod. Set up your dial indicator so it reads the thickness of the neck (zero it on the rod with no case and it will read the neck thickness. Holding the neck in full contact with the rod while under the tip of the indicator, rotate the case to check variation. You should be able to check quite a few necks in a short amount of time.

Mark the thinnest point on the neck of each case. See if there is a link between the thin point and the runout of the mouth (parallelism), and trim a couple of cases square to use to test if the neck flows at the thin point when fired. These tests should tell you all you need to know.

This gives me ideas except all I have is a dial. I dont have anything to mount it to. Its a random item I have from my sheetmetal days...

 

[DizzyJ]

 

[Member 34319]

Not really wanting to buy more inspection tools... I think I should…

Stop throwing yourself down the rabbit hole.

I've shot plenty of brass that was trimmed horribly by myself.

I'm not an expert, but I'd say you're overthinking some of this reloading stuff.

 

[P7M13]

Possible explanation : I had a bolt face that was out of square - not perfectly 90° with the barrel bore axis. I didn't worry about it because I figured 'law of averages', the case would be fired at a different position and the angle changed. With that gun, I encountered a few cracked case heads, which may be attributable to that uneven stretch. To confirm my thoughts, I took a fired case, put it on a machinist's stone (have three), and check it for alignment by using my Starrett combination square. Yes, you could see there was a non 90° attitude in the fired case.
I've since replaced that barrel, and the gunsmith faced off the receiver and bolt face. Problem not seen since.
--
If the sizing process is imparting the angle into your neck, it's likely you're binding on the upstroke as you pull your expander ball (most likely) or mandrel back through the case neck and mouth. You should feel that resistance. Try putting an ever so slight amount of lube on the die expander to see if that changes the outcome with a piece of brass.
I'm of the opinion, causing the misalignment when you push the case up into the die would show up in the shoulders and cause a case that won't fit a case checker.
Lastly, if you put a case into your case checker, and all that you see is that the neck edge is out of square, the case is parallel, but you're getting uneven stretch in the brass at the neck. Seems odd, but it's plausible.

 

[ageingstudent]

What would cause the rim of the neck to not be square, or more precisely, parallel to the base? Is this an issue to fix?


Photo isnt the greatest as I tried to get the light to show the gap. This is twice fired Nosler Premium brass and fully sized, I dont need to trim it but have been to square them up but it keeps coming back.

View attachment 1367943

Have you tried some powdered mica on your case necks before you size them? It looks like your expander ball is drawing the brass unevenly. If you use the powdered mica for a neck Lube you don't have to clean it.

 

[Koda]

Have you tried some powdered mica on your case necks before you size them? It looks like your expander ball is drawing the brass unevenly. If you use the powdered mica for a neck Lube you don't have to clean it.

I havent, I use Hornady Oneshot lube though.

So I have found the origin of the issue is with the brass supply. Unfired cases also show rim edges out of square.