223 Case Rupture - Headspace Discrepancy?

K

k Squared

New member
So...I'm banging away with my AR when a case fails to chamber. I eject the case and find this:
Ruptured%20Case%201_zpszvegyafq.jpg

I compare it to a normal spent case:
Ruptured%20Case%204_zpsyc0bgjl9.jpg

What could possibly have caused this?
I check the fired cases near me and find this:
Ruptured%20Case%202_zpshxy0sbfs.jpg

I assume the case fired before the malfunction tore apart, leaving the top half wedged in the chamber, and the next case was shoved into it.
This was reloaded ammo. I'd been using a small base sizing die. I had been reloading for my son, and didn't know his headspace measurement, so had the die set to its maximum depth.
I pulled out my trusty headspace gauge and found that I was sizing the cases to -.003" and my chamber was +.005” on the gauge.
Did I just work the case too hard, sizing it to minimum length and firing it in a maximum length chamber, or is there something else at work here?
 
I can't tell from the picture, but a jagged edge is bad brass (too hard, wasn't annealed), a clean edge is bad headspace (or brass fired one too many times -- I junk them after 8 firings).

Glad to see you safely detected the obstruction.

Edfardos
 
Did I just work the case too hard, sizing it to minimum length
Click to expand...
Yes. The front part of the 223 case was left in the chamber, because of a case separation. The next round jams into the remaining brass. Had it happen to me. When FL sizing, the shoulder is being pushed back to far. Its hard to get a good reading on fired brass. Its possible the head to datum can get shorter after firing, a less than maximum loading.
 
attachment.php


I got 8 gallons of mixed 223 brass at a gunshow for $62 ~ 10 years ago.
Every brand and condition imaginable.
I loaded up some ammo, should have been 35kpsi 35 gr Vmax 15 gr Blue Dot.

Two guys were in the middle of nowhere shooting prairie dogs and one runs out of ammo, and gets some of my ammo from the other guy's vehicle. In a Rem 700 223 the case blew. Then I get a call from 900 miles away that my ammo made them drive 200 miles to find a doctor.

I have determined it was bad brass. They guy that got it in the eye is now very fussy about only using Win brass that he bought new himself.

I wear eye protection when shooting targets or rodents. I do not wear eye protection when shooting ruminants, but they are reduced loads from higher works ups. And that brass is inspected if not new.
 
I check my new brass too. I have found defective brass many times, but you can only check so much by eye. Now that I think about it, down by the head is usually where I find defects.
 
Some years ago I was testing a string of 25-06 loads, on new W-W brass, when one round blew the primer. Luckily, I was chronographing, and the speed was normal, so the cause had to be a bad brass...soft case head... As to .008" setback on brass, it certainly will cause the brass to fail after very few loadings. If I set brass back to 'factory' specs, I do not plan on them ever being loaded again.
 
I got 8 gallons of mixed 223 brass at a gunshow for $62 ~ 10 years ago. Every brand and condition imaginable.
Click to expand...
:eek:
Handgun brass - yes, with inspection.
Shotgun hulls - probably.
Rifle cases - no, not like that.
 
I have to agree. I wouldn't buy or collect used rifle brass any more than I'd pick up that half empty bottle of tequila next to the doorstep. There, I said it.

I'm having a hard time deciding about that failure, but I tend to accept the defective brass.


A bolt gun like the 700 does have a small sectio.n of unsupported brass. Normally the brass is still supported by the barrel almost all the way to the rim. Note that it tore off just above the physical rim, and I see no evidence of a solid web. ?

It's really hard to know what I'm seeing, but that's really abnormal and I have never been shown a photo like that, to my recollection.
 
After tumbling in a vibratory case tumbler, I noticed some dull lines running around the circumference of some of my once fired factory ammo.

Cutting some of those in half reveled a thinning of the brass in that area.
Approximately 1/2 the thickness of the case wall.

I have seen this happen in 3 of my Ar's.

Also seen it with brass given to me that came from a piston driven Ruger, a SIG?, an AR pistol, and even in a bolt action rifle.

Also seen in brass picked up at the range.

Except for the picked up brass, I know this was all once fired factory ammo.

Seems to happen once or twice every 1000 rounds, except for PMC bronze ammo, that seems to happen more often.


8 PMC Bronze 223
1 PMC 5.56
3 Winchester Korea 5.56
2 Winchester USA 5.56
1 Fed 223 tactical
1 Lake City 5.56

I measured the length of some of it, and about 50% of those were less than trim to length.

I have not seen it with any of my reloads, whether twice fired or fired more than that.
 
It is caused by excessive headspace of the chamber, compared to the sized brass. The chamber is too long or the brass is too short. That also presents the key to the solution, if you hand load; just size the brass longer to fit the chamber.

-TL
 
It is caused by excessive headspace of the chamber, compared to the sized brass. The chamber is too long or the brass is too short. That also presents the key to the solution, if you hand load; just size the brass longer to fit the chamber.
Click to expand...

Or just bad habits; I am the fan of off setting the length of the chamber with the length of the case from the shoulder of the case to the head of the case.

Given the chance to sort cases by length as described by Clark:
I got 8 gallons of mixed 223 brass at a gunshow for $62 ~ 10 years ago.
Click to expand...
I can sort cases to fit the chamber.

Wait, I have 4,000+ 223 cases and I did sort them and I am one of a few reloaders that size a case to fit a chamber before firing. Again, there is nothing entertaining about pulling the trigger on a round when having no clue what is about to happen.

Most of my 223 cases came in a load of 23,000 cases I acquired in Yonkers NY.

F. Guffey
 
The crack in Clark's photo is strange as the crack is in the thickest part of the head .
I had been asked to analyse a failed 45acp case .There was a poorly formed area in the internal bottom of the case a that caused a fatigue failure through the head.
Perhaps Clark's was a similar failure .I would have to cut up and look at the inside of the case to see if it was a similar cause .
 
tangolima said:
Clark. Your picture looks like a out-of-battery ignition.
Click to expand...

+1


If you say bad brass, how did the base get larger than the chamber. It is borderline, as that might be the thicker head area held by the bolt.
 
The crack in Clark's photo is strange as the crack is in the thickest part of the head .
Click to expand...

True, the area that failed is the strongest part of the case, the part that failed is the unsupported part of the case, the part of the case that failed is in the area of case head protrusion. I just had an exhausting discussion with member that is reinventing everything. I suggested I want my case heads to have the ability to upset, I want my case heads to expand, I do not want my cases so brittle they split and or crack etc.. And then there is the part about ‘the more I fire a case the harder the case head gets' and then there is that infatuation with getting 40 firings out of ever case. Anyhow he just walks around with a snarl on his face condemning cases that will upset or crush with heavy/stout loads.

F. Guffey
 
8 ball:

Those rings are to be expected. It means that your brass is being stretched during firing. A bolt has a firm, solid action, and can tolerate even cases that are slightly oversized. An arr, however, must obviously have a slight looser fit because the return spring just isn't powerful enough to force a case into a chamber that it doesn't fit.

When an ar fires and specs are in variance too far, the pin will push the smaller case into the chamber until either the shoulder or extractor grabs it. The brass will then lock onto the sidewalls before the bullet leaves the casing, and the pressure will then push the case head back until it stops at the breach. If the condition is serious enough, an area towards the base will stretch and form a weak spot. Repeated sizing and firing will inevitably result in this ring weakening until the extror even firing it will tear off the case head at the ring.

This isn't as common on bolts, and seems to be worse with straight caused semiautomatic shoulder headspaced cartridges, especially if the chambers or brass are outsized.

When you find this ring on brass destroy it with a hammer. If you suspect a case, slide a hooked piece of fine steel wire into the case, and drag it back and forth. If you feel a catch near the head, you have a ring starting. Destroy ANY brass that shows signs of this weak spot. If you find lots of brass that seems to have that weak spot, Back your dies off a few hundredths at a time, nd set them where you are able to still get reliable functioning. This should minimize weakening the brass unless the problem is in the gun itself.

I wouldn't use range findings on a bet. The only used brass that I would ever think about using would be commercial once fired from a good source.

Maybe you're a blaster who can't afford to take those extreme precautions, but that's simply your decision, not mine, and you have already found a number of cases that were close to failure. This kind of failure is generally not serious, the gas just vents and the rifle can't be fired. Every shot fired has a slim chance of failure no matter what you do.There are dozens of things that increase the risk. Avoid things that increase that risk. Read up on reloading safety and follow the good advice that you find.
 
You must log in or register to reply here.
Back
Top