How long does it take?

[Bob3700]

My question is: How many firings does it take for the case neck thickness to stabilize? Do they ever? First, I use a Redding FL bushing die to size my cases, then use an inline/inside neck reaming die to establish my neck ID. . Once the brass ID has been reamed, it seems like after two firings, the neck IDs get smaller/ has inconsistent internal dimensions. In 6 mm cases, I size with a .268 bushing and my mandrel is .242. There should be very light drag on my mandrel after sizing but after 2-3 firings, there is more than a light drag. I figure the shoulder/ neck junction ( donut area) is thickening, but the mandrel oftentimes begins a heavier drag in the mouth / mid-case area. Cases are annealed after each firing.

I put the cases back in the inline reaming die and remove the inconsistencies and all is right in the neck tension world. If u take a lighted magnifier and look at the inside of a reamed case neck u can see the reamer is removing material from all of the high spots. I assume ( u know how they spell that) that brass moves during each firing and it has to go somewhere, so it moves into the thinner neck area.
It would seem that this is a common situation as it occurs across my different calibers/cases.

If u outside neck turn and then run the case over a sizing mandrel, u are moving those neck inconsistencies to the outside of the case. They are still there u just don’t see/feel them. Are they not still affecting ur bullet release? How many times after firing do u find uhave to “ clean up” ur necks?
It appears to me that this is just brass maintenance. Thoughts?

 

[Bill Norris]

According to Jack Neary brass continues to flow unevenly back into the necks at firing.

 

[Clancy]

It’ll never stop. That’s why I run .004 clearance and don’t get near the donut- and in the rare event I do neck turn, I redo them periodically.

 

[Bob3700]

According to Jack Neary brass continues to flow unevenly back into the necks at firing.

I believe that what I am talking about is exactly what Jack is referring to. The necks are ever changing and u either win generous clearances or set ur self ur for neck maintenance. I do like the inside/ in-line neck reaming as it keeps the neck ID aligned with the body of the case. Plus, it is very easy to keep necks in dimension..

 

[Gabe22BR]

First ting— …quit accelerating it by using a mandrel !!!
Turn it 1X
Shoot it
Anneal, size again
Turn again to clean up
Use bushing only after that
Trimming is required every firing- only a 40* shoulder slows that- less shoulder angle= more trimming

Brass flows every firing till it separates or primer pocket gives out…

 

[jackieschmidt]

I have 30BR cases that I originally turned to .0098, and after as many as 20 firings they still measure the same.

I do not pay any attention to the area down by the neck shoulder junction because the bullet never gets anywhere near it.

 

[sqrlgtr]

I have 30BR cases that I originally turned to .0098, and after as many as 20 firings they still measure the same.

I do not pay any attention to the area down by the neck shoulder junction because the bullet never gets anywhere near it.

My 30br brass is the same except they were turned 10 thou....Mine probably have more than 20 firings.... never been annealed either... I will have to cull one every now then thats harder to size than the others though...

 

[Bill Norris]

I have 30BR cases that I originally turned to .0098, and after as many as 20 firings they still measure the same.

I do not pay any attention to the area down by the neck shoulder junction because the bullet never gets anywhere near it.

This.

 

[Bob3700]

First ting— …quit accelerating it by using a mandrel !!!
Turn it 1X
Shoot it
Anneal, size again
Turn again to clean up
Use bushing only after that
Trimming is required every firing- only a 40* shoulder slows that- less shoulder angle= more trimming

Brass flows every firing till it separates or primer pocket gives out…

Trim every time? My brass only grows .005 or so after three or four firings. The Gerard trimmer can’t hold better than a couple of thou. OAL so for me that would not be a value add. The

 

[Gabe22BR]

Yeah I trim .003” short of my chamber- keep carbon ring down- using the ream your own holder for Giaurd.
Takes the “wobble trim” out of it- making it more.0015” tolerance…

 

[Straightshooter1]

I have 30BR cases that I originally turned to .0098, and after as many as 20 firings they still measure the same.

I do not pay any attention to the area down by the neck shoulder junction because the bullet never gets anywhere near it.

Ditto for me and my .308 and 6.5 PRC cases. I'm going on 16 firings with my PRC and the neck's thickness still measure .014 that I originally turned them to. While I also don't seat bullets down to the neck-shoulder junction, I recently took my pin gauges and measured down to see how much of a donut had developed. After running an expander mandrel to get the neck tension I'm after, the donut ID is a less than .001". . . maybe because I anneal after every firing. Even before sizing the neck, that donut wasn't much different from the neck's fired ID.

As often as I measure and track my case neck's thicknesses, I've just never seen my neck grow in thickness the way OP describes (only the donut). . . even for the likes of Federal brass.

What OP describes is what I'd expect from brass that isn't annealed where the necks work harden producing more springback after each firing; not that the thickness of the necks are actually thickening.