Starline 556 case head separation

[RabbitSlayer]

Good news, I got the case out with a brush easily and i see no evidence gas leaked into the chamber on the brass or with a borescope. I dont feel anything inside or outside the cases. I see a little change in color at that spot. I see similar lines on other fired brass from all my guns though.

 

[RabbitSlayer]

Is your chamber made to headspace virgin brass with .004" crish fit on closing the bolt. Or did the Smith just run a reamer in deeper to make it Ackley improved??

This matters a lot!
Post a pic of one of your formed pieces standing next to a piece of virgin brass

Virgin piece from same lot on left

 

[precision1]

I'm following would like to know outcome myself.
Please post op
We all go back to basic stuff but op definitely knows what he is doing.
Please keep us posted

 

[tommeboy]

That is where 223 brass always separates. Did you jam the bullet on the first firing? If you didn't there is your problem.

 

[rfwind]

Last season I had a Starline 5.56 case split lengthwise as shown in a previous photo. No more Starline for me

 

[SeabeeKen]

What happens when head space is wrong…
Takes path of least resistance

^^^^^^ My first thought. Bolt should close snug on a properly headspaced AI chamber. I always set my headspace with Manson HS gauges because they have the .004 crush built into them. That case stretched a lot for a reason. When properly done, AI case necks get shorter upon firing because the brass comes from the front to fill the chamber. This happens because the case head is against the bolt face. In your case, the firing pin drove the case forward and pressure drove the head back and stretched the case.

 

[jelenko]

That is where 223 brass always separates. Did you jam the bullet on the first firing? If you didn't there is your problem.

Interesting. Mine all come apart about 1/2" to 3/4" from the bottom - much farther down than shown.

 

[243winxb]

1st was a mid book load

The head to datum became shorter on firing. Case body expands outward, pulling neck & shoulder back.
Firing pin strike may set tthe shoulder back .006" depending on extractor type.

Then the full power loading streched the brass, till it separated.

Use 5.56 Starline brass? Why, its harder towards the case head. Your annealing may have stress relieved the brass towards the case head? A good thing.

https://apps.dtic.mil/sti/tr/pdf/ADA030722.pdf
Brass needed 1 more anneal to stop separations of Win brass in 5.56, auto. The extra anneal was done to the case body.

 

[SSchnd]

Newer Starline 556 from a known good XTC loader and shooter. not the first time I am hearing this either.

 

[jelenko]

Newer Starline 556 from a known good XTC loader and shooter. not the first time I am hearing this either.

Ewww.

I've got a LOT of Starline 223 and 556 brass. I mean, a LOT.

 

[Rick300]

I am having this exact problem with some Starline 223 brass formed to 20 Vartarg. I am very careful when forming to sneak up on the proper shoulder setting so it is NOT excessive headspace. I have made over 1,000 of other brands without this problem so I believe it is Starline specific.

 

[243winxb]

Starline Forming 223 brass

Why not use this to form different cartridges?

I would contact Starline Brass.

Since this is a basic case, and Starline has no control over how it is formed, we accept no liability and offer no warranty in its use or your inability to properiy form cases. .

 

[Rick300]

Because that brass is almost double what 223 brass is. I did call Starline and they said they don't know what is going on with that. They're sending me a 250 count bag as a nice gesture. Problem is I formed 1400 of them!

Edit to add that Starline is the only brand doing this. It's really a shame because their brass measure's out very consistent

 

[243winxb]

Looks like about .015" stretch. No wonder its coming apart.

 

[RabbitSlayer]

Newer Starline 556 from a known good XTC loader and shooter. not the first time I am hearing this either.

Wow that is disturbing.

All the concepts about the AI, headspace, and so on I fully understand. Everything has been what I expected with crush fit on factory ammo etc. I got the chamber super clean last night. I won't have time to torque it back on and check headspace again till probably tomorrow.

 

[RabbitSlayer]

I also checked the headspace change between the sized brass ready to load and the fired cases. The difference between them is mostly .001 and the max I could find was .002 between the shortest unfired and longest fired.

 

[243winxb]

chamber super clean

May not be a good idea. Lube brass, first firing? Post #12

Brass gets damaged on the very first firing, when stretch is excessive.

 

[RabbitSlayer]

May not be a good idea. Lube brass, first firing? Post #12

Brass gets damaged on the very first firing, when stretch is excessive.

I know to not leave lube in the chamber or on brass and that it causes excess bolt thrust. I got it clean to check headspace again. I dont want carbon in the shoulder area.

 

[RabbitSlayer]

Looks like about .015" stretch. No wonder its coming apart. View attachment 1650015

I just google 223 vs fireformed 223AI pictures. They look about the same to me. Am I missing something? Here are pictures of how its supposed to look.

223 Rem + 223 AI Cartridge Guide

223 Rem Guide for .223 Remington reloading, 223 Rem accuracy, .223 Rem hunting, 223 AI and 5.56x45 rifles. 223 Remington Brass, 22 bullets, powder, primers and loading dies for .223 Remington. Ballistics drop chart for .223 Rem, .223 Ackley AI, 2-250. 223 Remington Black rifle, service rifle...

www.6mmbr.com

 

[243winxb]

The damage is done on the first firing. The case may take as many as 2 more firing to separate.
Looks not important, measurements are.

I found that .014" head clearence/shoulder setback, will cause separations in the case body of 5.56 fired in a 5.56 chamber.