What happened here

[johnsons1480]

I finally got around to loading some LC brass I've been hanging on to. Took it to the range yesterday to do some load testing, and during my third string I had a case head separation. My load data was

LC '09 Brass

Remington 7 1/2 Primer

Ramshot Tac 23.8 gr

Sierra 77gr HPBT MK

Sierra list loads of 21.8-24.0, but Ramshot lists loads of 22.3-24.8. So as far as the Ramshot data goes, this is middle of the road. I've never had any issues shooting max loads of Varget out of this same rifle, so I'm confused by what happened here. The entire piece of brass extracted, but came out as two parts.

Also, I shot these rounds through my rifle as factory new M855 rounds, and I removed the crimp from the primer pocket. Any ideas on why this might have happened and how to avoid it in the future would be appreciated.

This is an AR15 with an 18" Rainier Arms Intermediate Length UltraMatch barrel. It was headspaced by the gunsmith who built it.

Picture of the case

Edited March 20, 2014 by johnsons1480

[Powder Finger]

can't see the pic but if the brass was sized with the shoulder pushed back too far can cause a separation even on 1st firing

[Dan Sierpina]

Did you trim the brass? It looks to have a serious crimp on the case mouth. As Powder Finger suggests over sizing can result in head separations. Your gunsmith may have checked the headspace, but not set it, unless he cut the chamber.

Another possibility is that the brass short to begin with. I mean that the shoulder dimension was short, not the case length.

[johnsons1480]

I will have to check some fired brass and make sure I'm bumping the shoulder no further than .005".

I did trim the brass to 1.755". The "crimp" you're seeing isn't a crimp, but it does look that way in the picture. I don't crimp my rounds.

He didn't set the headspace. I just meant that excessive headspace in the chamber isn't the issue at play. It's very possible that I bumped the shoulder too far back. I didn't realize that could cause a failure like this.

[johnsons1480]

Follow up question, is my rifle ok? The round landed on target, and chronoed at around the same velocity as the rest of the rounds in the string. Both pieces of the brass were ejected, and the next round fed. I quit shooting for the day after this happened.

[Powder Finger]

Should be ok just brush the chamber and look at it close.

[johnsons1480]

Thanks, I appreciate the help!

[dauntedfuture]

depending on the dies you could be crimping and not know it. Many rifle dies have a built in crimp so you can seat and crimp in one step. try adjusting your die higher and screw down the seater a little to compensate. I cant see the pics either.

[Powder Finger]

size not seat

[Alaskapopo]

I finally got around to loading some LC brass I've been hanging on to. Took it to the range yesterday to do some load testing, and during my third string I had a case head separation. My load data was

LC '09 Brass

Remington 7 1/2 Primer

Ramshot Tac 23.8 gr

Sierra 77gr HPBT MK

Sierra list loads of 21.8-24.0, but Ramshot lists loads of 22.3-24.8. So as far as the Ramshot data goes, this is middle of the road. I've never had any issues shooting max loads of Varget out of this same rifle, so I'm confused by what happened here. The entire piece of brass extracted, but came out as two parts.

Also, I shot these rounds through my rifle as factory new M855 rounds, and I removed the crimp from the primer pocket. Any ideas on why this might have happened and how to avoid it in the future would be appreciated.

This is an AR15 with an 18" Rainier Arms Intermediate Length UltraMatch barrel. It was headspaced by the gunsmith who built it.

Picture of the case

Once fired Lake city I am assuming and not new. Its not your load in once fired Lake city brass from most venders there are at least some cases mixed in that were fired through a SAW which is open bolt and excessively head spaced. I got a few like that myself on this last batch of Once fired Lake City I bought. That is why I only like new Lake city but its hard to find these days. Don't worry its not your gun. A way to find these cases ahead of time is to pull the ones aside that take more effort on the sizing stroke. 9 times out of 10 they are the ones fired through a saw.

Pat

Edited March 21, 2014 by Alaskapopo

[johnsons1480]

depending on the dies you could be crimping and not know it. Many rifle dies have a built in crimp so you can seat and crimp in one step. try adjusting your die higher and screw down the seater a little to compensate. I cant see the pics either.

I'm using a Forster Ultra Micrometer die. They don't crimp. The rounds aren't crimped at any point in my loading process

[johnsons1480]

I finally got around to loading some LC brass I've been hanging on to. Took it to the range yesterday to do some load testing, and during my third string I had a case head separation. My load data was

LC '09 Brass

Remington 7 1/2 Primer

Ramshot Tac 23.8 gr

Sierra 77gr HPBT MK

Sierra list loads of 21.8-24.0, but Ramshot lists loads of 22.3-24.8. So as far as the Ramshot data goes, this is middle of the road. I've never had any issues shooting max loads of Varget out of this same rifle, so I'm confused by what happened here. The entire piece of brass extracted, but came out as two parts.

Also, I shot these rounds through my rifle as factory new M855 rounds, and I removed the crimp from the primer pocket. Any ideas on why this might have happened and how to avoid it in the future would be appreciated.

This is an AR15 with an 18" Rainier Arms Intermediate Length UltraMatch barrel. It was headspaced by the gunsmith who built it.

Picture of the case

Once fired Lake city I am assuming and not new. Its not your load in once fired Lake city brass from most venders there are at least some cases mixed in that were fired through a SAW which is open bolt and excessively head spaced. I got a few like that myself on this last batch of Once fired Lake City I bought. That is why I only like new Lake city but its hard to find these days. Don't worry its not your gun. A way to find these cases ahead of time is to pull the ones aside that take more effort on the sizing stroke. 9 times out of 10 they are the ones fired through a saw.

Pat

They were once fired by me. I bought new M855 ammo a while ago, and shot some of it. These loads were made with that brass, so it was once fired by me.

[johnsons1480]

size not seat

I'm not following you

[Powder Finger]

depending on the dies you could be crimping and not know it. Many rifle dies have a built in crimp so you can seat and crimp in one step. try adjusting your die higher and screw down the seater a little to compensate. I cant see the pics either.

this, just so the topic stayed on track.

[johnsons1480]

depending on the dies you could be crimping and not know it. Many rifle dies have a built in crimp so you can seat and crimp in one step. try adjusting your die higher and screw down the seater a little to compensate. I cant see the pics either.

this, just so the topic stayed on track.

Got it, thanks for the clarification

[coordinator]

Do you keep a broken shell extractor with your kit?

I keep a broken shell extractor on hand for this. I've never had to use it, but I have loaned it out.

[johnsons1480]

I do not. The case completely extracted on it's own, and the next round chambered. I took this to mean I did something seriously wrong, so I packed up my stuff and came here to ask questions before I proceeded. I've never had a case head separation, so it scared the crap out of me.

[RPatton]

Inspect the other cases for signs of an incipient case head separation i.e. a bright ring around the case at about the same distance from the case head as the one you already have in two pieces. Moving the shoulder back too far during sizing has this effect: The firing pin strike will drive the round as far forward as possible, being stopped by the shoulder. The pressure spike will cause the the thinnest part of the case, the forward part, to expand and grab the chamber wall. The thicker part of the brass which will not be holding the chamber wall as tightly and will be forced to the rear by the internal pressure and stretch or separate the case. The stretching is what causes the aforementioned ring.

It doesn't have to be a hot load to do this if the shoulder has been pushed back too far during sizing. You don't mention checking your brass with a case gauge after sizing to ensure that they will not only chamber in a semi-auto but not chamber TOO deep. I use a Dillon case gauge to set the size die.

Be wary of range brass. I shoot range brass a lot but not when it matters.

[anm2_man]

To the OP - Maybe you should not worry about this problem. About a year ago I was shooting a bunch of LC M855, and when I got home I started sorting the brass. I came across a case that looked like yours, but it was not completely separated. It looked like there was a impurity when the case was formed. Now it shot just fine as it was originally loaded. But if I would of reloaded it, it would of had ended up just like the OP's. I know I took a picture of it, but I've looked, but can't find it. When I do I will post it here.

I shoot a beltfed in 30-06 and I use my reloads plus milsurp ammo. Its a good day if I can shoot 2,000 rounds and not have at least 1 case separation.

If you get a few more of these, then maybe there is a problem with your rifle.

[JPeel]

When I was developing loads for my new seekins I started to get some separations on Winchester brass on my higher, but well within normal, loads. I checked the rest of the unfired brass for signs of failure, none found. Checked headspace, all good. Then I realized that I hadn't adjusted the gas block on the new rifle. Got that set correctly and no more separations. So maybe you are over gassed?

[bigedp51]

johnsons1480

The military doesn't sell loaded M855 ammunition, "BUT" Federal does sell ammunition loaded with Lake City cases that failed military quality control inspection.

And a over gassed AR can have the bolt moving to the rear while pressure is still in the barrel, meaning the case may be still gripping the chamber walls as the bolt starts moving to the rear and allows the case to stretch.

I use the RCBS case mastering gauge to measure thinning in the base web area of the case, and any thinning is measured in thousandths of an inch.

You can't see it in the above photo but the gauge has a bent rod with a small pointed end just below the gauge tip and reads very accurately.

I don't have your cases in my hand but my guess is a defective case that failed military quality standards.

Below a Colt Field headspace gauge, 1.4376

Below the same Colt gauge in my " adjusted and calibrated" Hornady cartridge case headspace gauge.

Below a fired case from my AR15 16 inch carbine.

Below the same case after sizing and .003 shoulder bump.

You will not have case head separations if you inspect your cases and set up your dies for the proper shoulder bump.

And ammunition with the Federal name on it wasn't made and loaded at Lake City Army Ammunition Plant.

[bigedp51]

Military 5.56 cases are made to higher standards than commercial .223/5.56 cases and military cases are harder in the base area to better withstand larger diameter and longer headspaced firearms. If the cases fail military quality control inspection for any reason they are sold off and then Federal loads them and sell them to us.

As long as you didn't bump the shoulder back too far you did nothing wrong and shit happens.

The cases below were fired in a brand new Savage .308 rifle, after testing these cases there was no damage done to the rifle.

In simple terms shoulder bump at the front of the cases is called head clearance at the rear of the chambered cartridge.

When the case is fired pressure pushes the primer to the rear until it contacts the bolt face. As chamber pressure continues to build the brass stretches to meet the bolt face, a case with excessive shoulder bump and head clearance can stretch to the breaking point.

If you really want to learn about headspace, head clearance and case head separations then buy a British .303 Enfield rifle. A Enfield rifle at maximum allowable headspace can have .017 head clearance.

Edited March 30, 2014 by bigedp51

[anm2_man]

Bigedp51 - Question for you. The chart that is in the previous post showing the brass endurance, was the brass shot in a bolt or semi auto gun ?

[johnsons1480]

I'm fairly sure that I bumped the shoulder too far back. I am good about bumping back .002" on my bolt rifles, but I threw caution to the wind and adjusted the die according to the mfg. documentation this time. I now have some fired cases from this firearm, and will be able to measure and adjust from there.

[bigedp51]

Bigedp51 - Question for you. The chart that is in the previous post showing the brass endurance, was the brass shot in a bolt or semi auto gun ?

The .308 cases were fired in a new Savage bolt action rifle and the cases were resized as per the dies instructions with the press reaching cam over. The problem with the article was the rifles exact headspace was not given nor was the amount of shoulder bump given. So the amount of head clearance was unknown and resizing case life was a ballpark estimate. Meaning we didn't know how far the cases were stretching to meet the bolt face when fired.

Edited April 1, 2014 by bigedp51