View Full Version : How did this happen?
http://i.imgur.com/ZeF8Z4g.jpg
A friend's Sig 716 produced this from factory ammo of some sort. It bent his firing pin retaining clip, but otherwise no damage.
Is that the anvil?
Is that a pierced primer and the anvil came through? Thats what it looks like. I know you already thought that, but thats what it looks like. Can you punch the primer and post more pics?
What ammo is that? Got a federal head stamp, but I didnt think the GMM has the year date stamped on the head like that.
Is that a pierced primer and the anvil came through? Thats what it looks like. I know you already thought that, but thats what it looks like. Can you punch the primer and post more pics?
What ammo is that? Got a federal head stamp, but I didnt think the GMM has the year date stamped on the head like that.
I actually don't have the brass but I'll ask for it. He said he doesn't known where the ammo came from, he must have bought it years ago apparently.
Ill just say gas guns are notoriously hard on brass and loads that would work well in bolt guns will mysteriously pierce primers and tear rims off in a gas gun. I know Sig 716 is a piston gun, but same concept.
Ill just say gas guns are notoriously hard on brass and loads that would work well in bolt guns will mysteriously pierce primers and tear rims off in a gas gun. I know Sig 716 is a piston gun, but same concept.
Pistons ARs are even worse offenders in this regard, with no direct impingement unlock assistance.
Did it cycle normally? When was it noticed? Just asking out of curiosity - I don't have much to add regarding load pressure and such. Not my area.
I've never seen anything like that. Did he check out his firing pin (for damage)?
I've never seen anything like that. Did he check out his firing pin (for damage)?
Yeah firing pin was ok as far as we could tell. But here's the retaining pin:
http://i.imgur.com/SiJAC6M.jpg
I think the overpressure not only pushed the anvil out through the primer, it forced the firing pin back so hard that the retaining pin was badly bent. But that part took the brunt of the force it seems.
Pistons ARs are even worse offenders in this regard, with no direct impingement unlock assistance.
Did it cycle normally? When was it noticed? Just asking out of curiosity - I don't have much to add regarding load pressure and such. Not my area.
It didn't eject if I recall correctly. Also there was apparently a lot of gas or smoke. We noticed immediately.
http://i122.photobucket.com/albums/o254/bigedp51/piercedprimer-2_zps2d386fad.jpg
http://i122.photobucket.com/albums/o254/bigedp51/piercedprimer-1_zps292b54b8.jpg
http://i122.photobucket.com/albums/o254/bigedp51/primersa-1_zps144ecb5f.jpg
When the case shoulder is bumped back too far during resizing it creates too much head clearance or the air space between the rear of the case and the bolt face.
http://i122.photobucket.com/albums/o254/bigedp51/HEADCLEARANCE-a_zps1a9a1011.jpg
When the case is fired the firing pin drives the case forward until the shoulder of the case contacts the chambers shoulder. The cartridge goes bang and the primer is forced out of the primer pocket flowing back over the firing pin. When this happens the firing pin acts like a cookie cutter and punches the firing pin dent out of the primer.
http://i122.photobucket.com/albums/o254/bigedp51/HeadClearance_zpsf30a3af1.gif
This can be also aggravated by high port pressure and the bolt unlocking while pressure is still in the barrel and pushing the primer further out of the primer pocket.
This is not just a problem on gas operated rifles and can also happen to any rifle with excess headspace or cases that had the shoulder pushed too far back during resizing. I have one .223 die that will push the shoulder back .009 shorter than a GO gauge if adjusted to contact the shell holder. This could cause aproximatly .012 head clearance and a pierced primer, there is a reason why the military crimps it primers. And the case pictured in the OPs post doesn't look like a crimped primer so it may be a reload.
http://i122.photobucket.com/albums/o254/bigedp51/piercedprimer-2_zps2d386fad.jpg
http://i122.photobucket.com/albums/o254/bigedp51/piercedprimer-1_zps292b54b8.jpg
http://i122.photobucket.com/albums/o254/bigedp51/primersa-1_zps144ecb5f.jpg
When the case shoulder is bumped back too far during resizing it creates too much head clearance or the air space between the rear of the case and the bolt face.
http://i122.photobucket.com/albums/o254/bigedp51/HEADCLEARANCE-a_zps1a9a1011.jpg
When the case is fired the firing pin drives the case forward until the shoulder of the case contacts the chambers shoulder. The cartridge goes bang and the primer is forced out of the primer pocket flowing back over the firing pin. When this happens the firing pin acts like a cookie cutter and punches the firing pin dent out of the primer.
http://i122.photobucket.com/albums/o254/bigedp51/HeadClearance_zpsf30a3af1.gif
This can be also aggravated by high port pressure and the bolt unlocking while pressure is still in the barrel and pushing the primer further out of the primer pocket.
This is not just a problem on gas operated rifles and can also happen to any rifle with excess headspace or cases that had the shoulder pushed too far back during resizing. I have one .223 die that will push the shoulder back .009 shorter than a GO gauge if adjusted to contact the shell holder. This could cause aproximatly .012 head clearance and a pierced primer, there is a reason why the military crimps it primers. And the case pictured in the OPs post doesn't look like a crimped primer so it may be a reload.
Thanks for that. But that's not a hole in the primer. I mean there is a hole, but it isn't empty.
Do you remember the story about the little dutch boy with his finger in the dike? The primers anvil is the little Dutch boys finger plugging the hole in the primer.
If your too young to remember the little Dutch boy then think of a cork in a wine bottle. ;)
"BUT" if I remember correctly gallon jugs of Bali-Hai 68, MD 20-20 and Ripple had a screw on tops. :alcoholic:
http://i122.photobucket.com/albums/o254/bigedp51/Boxer-Primer_zps2da9c2c8.jpg
Now go back up and look at my first top photo and you will see the tip of the anvil plugging the hole in the primer.
Thanks for that. But that's not a hole in the primer. I mean there is a hole, but it isn't empty.
There's no swipe on the case head... so it doesn't appear to be excessive pressure. I wonder if the primer anvil wasn't a defect or if the priming compound wasn't caked in weird.
It looks like something defective in the primer pushed that anvil back through the cup... striking the firing pin and driving it back into the retaining pin.
My first thought was that the primer flash hole in the brass was missing, but if the round went downrange, you can rule that out.
If you can remove the primer, let us know if the flash hole appears to be normal, the correct size and not obstructed.
If you are certain the projectile went down range, it could be that the primer flash hole is too large, but that is rare with factory ammunition. If it was a reload, someone may have gotten a little too aggressive while cleaning out the flash hole when prepping the brass.
1) I have seen this malfunction when the firing pin protrusion was too long on a Mauser. The firing pin punched the primer, then the hot gas pushed primer material back into the firing pin hole. We had a devil of a time getting the brass to come out of the action after the bolt was completely out of battery.
2) I have also seen this malfunction on a AR-15 when someone reloaded with powder that had a much slower burn rate than recommended propellants. Think magnum rifle powder burn rate in an auto loader.
My first thought was that the primer flash hole in the brass was missing, but if the round went downrange, you can rule that out.
Yeah... could have been partially obstructed. This or a messed up primer.
A over gassed rifle still has pressure in the barrel as the bolt starts moving to the rear, and this pressure can cause the anvil to move to the rear and plug the hole in the primer cup.
The more head clearance you have the more likely the primer will be punctured, then if you add a slower burning powder the port pressure will be higher along with higher remaining pressure in the barrel pushing on the primer.
Chamber pressure pushed the primer to the rear and the anvil plugged the hole in the primer. In an Enfield forum the same thing happened and the cocking piece/firing pin was driven forcibly back and cut the shooters hand.
Good info and pics here..
The case appears to be Federal Xm193 Mfg'd in 2011. All of my brass marked FC has a date stamp. As stated earlier, check the firing pin for defects or replace it to be safe since it's so cheap along with the retainer.
The case appears to be Federal Xm193 Mfg'd in 2011. All of my brass marked FC has a date stamp. As stated earlier, check the firing pin for defects or replace it to be safe since it's so cheap along with the retainer.
My psychic ability makes me think you meant the cheaper Federal American Eagle brand. :stop:
http://i122.photobucket.com/albums/o254/bigedp51/193nato001_zpsf7b50cad.jpg
http://i122.photobucket.com/albums/o254/bigedp51/193nato002_zps3c5d9286.jpg
The case appears to be Federal Xm193 Mfg'd in 2011. All of my brass marked FC has a date stamp.
Its .308, not 5.56. Sig 716 is a .308.
Only date stamped cases I have seen in .308 were LC cases, but I guess Federal probably makes some 7.62x51 cases. None of my Federal GMM cases have been date stamped.
I'd chalk this up to a single defective round or primer fluke. If you get the case from the guy, you could punch the primer an check out the anvil and flash hole.
This looks like the same issue (https://www.m4carbine.net/showthread.php?152905-Excessive-pressure&highlight=) I was having with my PWS and 7.62x51mm FGMM (same load as your friend? The brass looks the same). PWS said my firing pin was protruding from the bolt face too much when they fixed my rifle, but it also seemed to be excessive pressure since many members here said that they find 7.62x51mm FGMM to be a hot load.
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