Case head separation on 9mm pistol caliber carbine

[10xsllc]

Had 2 on a new build head space is good what else can I look for

 

[std7mag]

Define "headspace is good".

Verify powder & charge weight with bullet & COAL.

 

[Geronimo Jim]

Winchester brass?

 

[David Milisock]

Had 2 on a new build head space is good what else can I look for

More information would be good. Factory rounds?

 

[dantiff2]

It’s very easy to over pressure a pistol caliber carbine!

 

[Walt Krafft]

New brass, used brass, factory ammo, reloads, gas port size?

 

[Randall D]

Had that happening on a friends 20 practical AR. Determined that it was being caused by the bolt unlocking and ejecting too soon. Not sure if it applies to your situation, but the guy that that had it determined that it was from a combination of buffer spring and possibly pre-ignition.

 

[stymie12000]

What brand of brass? Stepped cases are a big problem in 9mm carbine.

 

[Lucky6547]

I didn’t have separation issues, but I was getting soot on my cases cause the bolt was opening too fast. Got a 9.6oz buffer and a +15% 308 spring and that issue has gone away.

 

[chop house]

Had that happening on a friends 20 practical AR. Determined that it was being caused by the bolt unlocking and ejecting too soon. Not sure if it applies to your situation, but the guy that that had it determined that it was from a combination of buffer spring and possibly pre-ignition.

i am curious. do you have any more details? buffer spring too light? over gassed / port too large? pressure in barrel not dropping to safe level before unlocking? thanks

 

[acloco]

Pictures and need the answer to the above questions posted by other members please.

 

[Walt Krafft]

Just looked at my Rock River, it is blowback rifle. There is no gas system. What is yours?

 

[stymie12000]

Just looked at my Rock River, it is blowback rifle. There is no gas system. What is yours?

Most, if not all AR9 are blowback. The SiG MPX is gas. I don't know if any other platform is gas for Pistol Caliber Carbine (PCC)

 

[shoot4fun]

For years you could scavenge 9mm range brass, tumble, inspect, reload and enjoy. Then this thing the USPSA crowd likes to call 9MM Major came along. Shooters bought once fired processed brass, stuffed it full of powder and hammered a bullet in on top. They all admitted to the :shoot it once & leave it on the ground" philosophy. It was basically ruined. Along comes a scrounger and makes a fabulous find. Then someone gets head separations.
I suffered a few head separations in my M&P9. The first I chalked up to Murphy but the second and a third it was time to start searching for the cause. It was a tired recoil spring. As soon as that was corrected no more issues.
All, to my knowledge, 9mm AR's are blowback guns. The possibilities for this type issue abound.
Brass failure, FOB (fire out of battery) over pressure (maybe your gun is jamming bullets back in the case during cylcling and spiking pressure.
Just way too many possibilities without any more info on the OP's part.

 

[10xsllc]

New brass, used brass, factory ammo, reloads, gas port size?

used bass,reloads no gas ,blow back 9mm

 

[10xsllc]

Define "headspace is good".

Verify powder & charge weight with bullet & COAL.

i have good

 

[10xsllc]

I didn’t have separation issues, but I was getting soot on my cases cause the bolt was opening too fast. Got a 9.6oz buffer and a +15% 308 spring and that issue has gone away.

that is what i have been thinking ,will try thank you

 

[10xsllc]

For years you could scavenge 9mm range brass, tumble, inspect, reload and enjoy. Then this thing the USPSA crowd likes to call 9MM Major came along. Shooters bought once fired processed brass, stuffed it full of powder and hammered a bullet in on top. They all admitted to the :shoot it once & leave it on the ground" philosophy. It was basically ruined. Along comes a scrounger and makes a fabulous find. Then someone gets head separations.
I suffered a few head separations in my M&P9. The first I chalked up to Murphy but the second and a third it was time to start searching for the cause. It was a tired recoil spring. As soon as that was corrected no more issues.
All, to my knowledge, 9mm AR's are blowback guns. The possibilities for this type issue abound.
Brass failure, FOB (fire out of battery) over pressure (maybe your gun is jamming bullets back in the case during cylcling and spiking pressure.
Just way too many possibilities without any more info on the OP's part.

thanks for information, brass is from range i am also thinking spring and buffer

 

[243winxb]

fire out of battery

See photos here. COL to long.

 

[Hoser]

One cause of the "stepped" brass. There is a step inside some brass that prevents bullet setback. That step also makes a weak point in the brass and I have seen a lot of brass rings left behind in chambers.

Cull that garbage out and you will be happier.