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Starline 6mm ARC issue

DukeDuke

I'm shooting starline brass with 105 hybrids and cfe223 at 2700 fps in an ar, single feed,
col is 2.330. FL sized and trimmed every time. After being fired 5 times the necks of some cases got cracks in them. I wonder why that might be. My 223 starline has 11 firings with no issues, in an ar as well.

Thank you!
 

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I have not stayed at a Holiday Inn and I'm not expert on this.
I have recently read that split necks primarily are caused by stress corrosion cracking => any chance that the 6mm brass has been handled/processed differently or the barrel is cleaned with anything containing ammonia?
 
Classic textbook fatigue cracks.

Unusually, but not impossible, to see, in my experience, only after five firing and sizing even without annealing.

If you are using a conventional F/L die, how much drag are you experiencing on the sizing button? If excessive, you could be over working the case neck. Standard sizing dies tend to oversize the neck, and the expander buttons tend to be too large creating a high stress condition on the necks. At least that has been my experience with RCBS dies.

I do not anneal, but I get 15 to 18 reloads (223 Rem) out of case but I have a series of expander assemblies (various diameters) that I can use to customize a minimal drag on the neck for each rifle and brand of cases I use. Also, each sizing button is polished with very fine emery cloth to a smooth glass like finish to reduce drag.
 
DukeDuke said:
Thank you for replying!
I understand the annealing and the die expander button part , why 5 out of 50, 45 cases are fine.
Click to expand...
In my experience, starline does not anneal their brass very well. At least in the brass I have bought from them. My guess is, those cases that cracked did not get enough annealing at the starline factory. A QC issue.

The other possiblity is there are going to be more out of those 100 that crack in your next firing if the remaining are not annealed. Maybe the whole lot were poorly annealed and those were just the first 5 to go.
 
The cracks are indeed fatigue cracks associated with excessive hardness of the neck/shoulder region. And it is possible that SCC could be in play.

It is likely that the major issue is resizing with a standard FLS die. These dies tend to overworked the brass more than necessary and it may also be partially due to a large chamber neck dimension. Annealing is the simplest solution to prevent this problem.
 
Doom said:
The cracks are indeed fatigue cracks associated with excessive hardness of the neck/shoulder region. And it is possible that SCC could be in play.

It is likely that the major issue is resizing with a standard FLS die. These dies tend to overworked the brass more than necessary and it may also be partially due to a large chamber neck dimension. Annealing is the simplest solution to prevent this problem.
Click to expand...
I agree with this. I recently had a friend using standard FLS and his brass failed prematurely. We're both using Starline 6ARC brass. I use bushing die and no expander, none of the problems he's having.
 
I'm getting the same cracks on the second firing of of my starline 6.5 Grendel brass.

Update: My problem appears to be over working the brass. My fired brass is running about .294" at the case mouth, after sizing it's .283-.284".
 
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A few years ago, a friend was having the same problem using Grendel brass for several different cartridges and guns. In each case we tracked it down to overworking the brass. In one cartridge there was a .022 difference in diameter between fired neck size and what a factory loading die was squeezing it down to.
 
Walt Krafft said:
A few years ago, a friend was having the same problem using Grendel brass for several different cartridges and guns. In each case we tracked it down to overworking the brass. In one cartridge there was a .022 difference in diameter between fired neck size and what a factory loading die was squeezing it down to.
Click to expand...
The 22arc die set I have (Hornandy) was stupidly rough internally and severely over worked the necks so I honed and polished it to get it in reasonable shape.

I hope to replace it with a body die and Lee collet someday.
I anneal after every firing as well.
 
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