Over pressure?

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HankC

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Picked up some brass at the range, noticed two 223REM FC brass have blown primers, raised ejector marks and bent rims. Obviously from the same rifle. From the bent rims, I would think they were out of semi-auto, probably AR. Is this the 5.56 fired in 223 chamber thing? FC should be 223 REM spec and I don't think they make ARs in 223 chamber anymore. The side wall also shows a ring 3/16" above the base. I have not seen 223 brass this bad before! Definitely over pressure, but what caused it? They are factor loads since primer crimps still intact.

FC223%20overpresure_zpslaxrzvlz.jpg
 
Someone reloaded them way too hot? My guess since I don't see a crimp

Edit: I see you indicate there's a crimp, it just doesn't look like it to me in that pic, but I'm on my phone.
 
FC marked like that is generally 5.56 spec; it doesn't say .223 Rem. I've had Federal XM193 with that headstamp. Looks to me like the crimp has already been removed (reloaded at least once) and definitely overpressure for what it was fired in. Aside from the blown primer, the heavy ejector and extractor marks give it away. Certainly not reloadable at this point of courst...

I see AR barrels chambered for .223, generally only match/target and varmint models - in fact I own a couple....but the Wylde chambering seems to be much more common these days.
 
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The "ring" you see at the primer pocket mouth is not a chamfer, it is a circle crimp mark seen on FC brass. Honestly I don't know for sure if it is factory or reload. I assume they are factory loads since the crimp marks still there. Reload will need to remove the crimp and typically see a chamfer. Swaged? Does the crimp mark remain if swaged?
 
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HankC said:
The "ring" you see at the primer pocket mouth is not a chamfer, it is a circle crimp mark seen on FC brass. Honestly I don't know for sure if it is factory or reload. I assume they are factory loads since the crimp marks still there. Reload will need to remove the crimp and typically see a chamfer. Swaged? Does the crimp mark remain if swaged?
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I use the RCBS swaging tool and I have it set to lightly remove the crimp in the primer pocket. The crimp in my brass after swaging looks similar to the brass in your photo. I suspect that the brass you found has indeed been reloaded.
 
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Ive seen brass like that in my own handloads, when i was pushing things. Either extractor or ejector marks would have me backing off atleast 1/2grain
 
Woof. Definitely over-pressure.

The side wall also shows a ring 3/16" above the base
Click to expand...

That is probably the beginning of case head separation. Another sign of over pressure, or several reloads on a single case.
 
Probably going to have to Locktite the primer into that for the next reload. . .

Maybe someone seated 77gr over a 55gr-appropriate charge. Swaging the pocket instead of reaming will leave a visible crimp.
 
That's a train wreck that didn't happen. It is almost certainly from a semiauto from my read on the bent rim. It could be from anything else if the case stuck in the chamber and had to be beaten out by maybe pounding on a bolt handle. Either way, it was way too hot. Primer got all the way out of the case so hot gas was in the action and all around the shooter no matter what gun it was. They are lucky that it didn't result in a case head separation by ripping the head off, a destroyed rim and stuck case, or even a weapon failure. That defined of an extractor mark indicates huge pressure.
 
Based on your pictures, I'd guess the cases were fired in an AR and could well be factory ammo, as I has similar experience w/a batch of XM193 ammo in an AR designed to handle 5.56 or 223 ammo several years ago. Did a lot of work on the problem and came up with some answers. Your extractor and ejector imprints are identical, except a bit more extreme, than those made by my rifle.

1. This particular batch of ammo, although advertised by a very large distributor as factory ammo, used different headstamps.

2. Contained a wider variation in powder charges than I would think normal.

3. Decided that the LC cases (someone said Federal has the contract to operate LC facility now) were softer than NATO stamped cases (probably in part due to hardening of brass which resulted from the nato stamp and the fact that NATO cases also had crimped primers).

4. Bullet seating depth varied a great deal more than one would think.


Found that by seating bullets a bit deeper (producing a bit of freebore) reduced pressures sufficiently to resolve the problem.

The following is my first post and a discussion follows with more details and pictures at the link below, if interested.

Blew a primer in my Bushmaster Predator today. Temperature was in the low 90's, ammo had not been in sun and barrel was not hot. It is supposed to have a Wilde chamber and handle both .223 and 5.56 ammo.

Previously had fired only handloads in the rifle, w/o any problems.
Purchased some American Eagle XM193BL, 55 gr. FMJ 5.56 ammo and the fourth round blew a primer. The problem became apparent when the 5th round wouldn't chamber. Tipped rifle and it fell out, so tried to chamber another round and bolt still wouldn't close, but this time the round stayed in chamber. Dropped bolt again to try to catch and eject 6th round unsuccessfully. That's when I discovered the blown primer. It was wedged between ejector and rim around bolt face:

Untitled-3.jpg

At this point I felt quite fortunate that I did not have a slamfire as the primer on bolt face slammed against head of loaded rounds 3 times before I realized what the problem was!

On closer examination of the ammo, I find at least two different cases have been used (only opened one box so far).

The two cases used are: LC 11 w/o NATO symbol and no primer crimp, and LC 11 w/crimped primer and NATO symbol. I suspect the cases w/o NATO symbol to be softer brass of the two because both of those cases show ejector indentation on case head, one blew primer, other didn't.

Here are case stats on the 5 fired rounds.

LC 11 w/o NATO stamp, blew primer: Exp. ring = .377", case wt.= 92.6 gr.
LC 11 w/0 NATO stamp, no blown primer: Exp ring=.376", case wt.= 93.0 gr.
Both cases showed distinct ejector imprint on case head.

Untitled-5.jpg

Three LC 11 w/NATO stamp, no blown primers: All three Exp. rings=.375", case wt. 92.0; 92.7; 92.7 gr. respectively w/no ejector marking on case head.

Checked a couple of WW cases which have been fired ? times w/warm handloads and case exp. ring measured .3745" on both. Primer pockets still snug.

Anyone else have similar problems?

Regards,
hm

http://img.photobucket.com/albums/v476/hm1996/AR15 Blown Primer/Untitled-5.jpg
Click to expand...

Regards.
hps1 (hm)
 
Way over pressure, has nothing to do with how the gun is gassed if it's an AR.

Probably going to have to Locktite the primer into that for the next reload.
Click to expand...
I am assuming that was a joke.
Ive seen brass like that in my own handloads, when i was pushing things. Either extractor or ejector marks would have me backing off atleast 1/2grain
Click to expand...
If you have blown primers and swaged the case into the hole for the ejector you did not work up slowly or ignored other signs of pressure before you did. One should never "work up" to the pressure shown in the pics.
when i was pushing things.
Click to expand...
No doubt, y'all be careful out there.
 
I've had some that looked similar from an AR with a light semi-auto BCG and std buffer/spring. Not that extreme but close. Primers were still in place but very flat. The load was not maxed out. I installed a heavy buffer (H3) with a heavy spring and the same loads ceased to show these pressure signs. The ejection went from 1 oclock to about 3:30.
The next step would have been a heavier full auto bolt carrier but I stopped while I was ahead. YMMV

Many times it's just all about the timing with AR's. The heavier components slow the operation down a couple of milliseconds and insures proper operation. Over-gassing, a carbine-length gas system, and a light reciprocating assembly causes the bolt to unlock too soon and the extractor tries to pull the case from the chamber while chamber pressure is still too high. The case is still expanded in the chamber and "welded" to the chamber walls, causing the extractor to try and pull a piece out of the case rim. Then the unlocked bolt may leave the case momentarily when the extractor slips off the deformed rim and the pressure in the case blows the primer out. Once the pressure drops then the case will loosen it's grip in the chamber and come out easily.

I have also had Federal brass -- ONCE FIRED, by me -- that had such a loose primer pocket that the new primer would fall out if I bumped the newly-primed case on the edge of my workbench. If the primer puts up NO RESISTANCE when you prime cases it's too loose.
 
As walkalong said, marks like those only appear well after youve gone beyond safe limits.
I know, ive done it intentionally, and i sure as hell wasnt behind the gun firing the rounds. Just a bit more after seing marks like that a case came completely apart....in small cases its take surprisingly little extra powder or deaper seeting to find out the hard way youve been riding the line, whqt i played with went fine to boom in a little over .5 grain
 
I've shot dozens of 7.62 NATO M60 arsenal spec proof loads in Garands and different bolt guns. Their case heads were virtually undistinguishable from normal max safe M80 ball loads at 50,000 CUP (~62,000 PSI). Most folks looking at them said they were "just fine and safe" to "maybe a little warm, but still ok to shoot." Typical proof pressure was about 67,500 CUP (~85,000 PSI).

Cartridge brass typically starts to extrude back into bolt face cutouts at about 70,000 CUP (~90,000 PSI). Now go back and look at those case head pictures.
 
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there's no way to know this but what powder do you figure this guy used (maybe by mistake) to reach that pressure? Most of the powders I've used that are common to .223 would be hard to cram enough into a case to cause that, right?
 
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