Diagnose this kaboom

[CrashDodson]

Sig X5 shooting reloads using once fired brass.  When the round went off it was very loud...more like an explosion than a gunshot.  Shooter was peppered with stuff, strong hand was black in the webbing of the hand.  The x5 extractor was no where to be found, but seemed to be the only damage.  The head of the case sheared off clean, almost like it was sawed off.  The rest of the case had to be pried out of the barrel but it does not look damaged.  

On this x5 if you slowly let the slide move forward it will stay slightly out of battery.  Do you think this was an out of battery ignition?  Double charge?  bad case?  Look at the marks on the head of the case, its like extractor slammed into the back of the case?  

Edited September 18, 2019 by CrashDodson

[Yondering]

IMO the out of battery condition is at least a possibility, but either way high pressure was a factor there. Note that it's CBC brass, which has smaller internal capacity which raises pressure. With the long internal taper in CBC brass, it's possible a 124gr or heavier bullet caused a bulge in the brass around the bullet base which may have wedged in the chamber, raising pressure even further. That also could have caused a slightly out of battery situation before ignition, with the case sticking in the chamber and adding extra resistance to the barrel/slide lockup.

 

I personally do not like lightweight springs in striker fired guns for this reason. I know many other people use them without issues, but...

 

Notice the firing pin swipe through the primer and into the case (right through the "CBC" - case head in your 3rd pic is oriented upside down); that slide unlocked VERY quickly. OOB situations can cause that.

 

Any details you can share about the load? What bullet weight? Minor or Major load?

Edited September 18, 2019 by Yondering

[CrashDodson]

The rounds before the pop chronoed at around 130-132 PF.  These were 3.5G tightgroup with a 135 Grain Berrys bullet 1.135 OAL

Edited September 18, 2019 by CrashDodson

[Ssanders224]

Google around a bit. 
Case head separations / web ruptures are proving to be too common in 320s & X5s. 
Notice the amount of case that is unsupported in the photos. Then notice how supported the case in the Bar-Sto replacement barrel. 

I have no idea why Sig chose to design the chambers this way, and obviously they don't think it's an issue. 

[HesedTech]

Hmm could have been a combo of the barrel and overcharge. 
 

The marks on your from the slide are huge compared to the others posted.  
 

You didn’t mention your reloading process, press and such. 

[CrashDodson]

These rounds were loaded by someone on a M7 Revolution with all the gizmos.  Is an overcharge still possible...sure.  Im just interested if anyone thinks it could be a out of battery issue/case support issue.  I have never personally witnessed an overcharge, unless that is what happened here.  I have had case heads separate in my limited guns shooting .40 before but they did not sound like this, they were actually quieter than a normal round and I was peppered with a lot more unburnt powder.  

 

It may be a situation where there is not a way to prove one way or the other.  What I dont understand is these markings on the case.  

 

 

[MikeBurgess]

I would say double charge, the case head imprint from the breach face indicated extreme pressure was involved not just a case rupture

[dansedgli]

Overcharged case. 

 

Look at those marks on the case head. Damn. 

 

Also s#!tty barrel support doesnt help. 

 

Mine would bulge cases quite often but case heads always looked normal. 

[muncie21]

Can't tell for sure if the discoloration (green) on the case (10 O'clock position in the pic) is corrosion or something else.  If it's corrosion, perhaps there was a small crack already, so rather than an over-charge the case separation caused the significant impressions seen on the case head

 

Edited September 18, 2019 by muncie21

[zzt]

Just another reason not to use Titegroup.  It is junk.  It's hot, dirty and BRIDGES in the powder drop tube.  That is what I think happened here.  Powder bridged and it, plus the new charge dropped into the next case.  One underpowered round and one kaboom.  Titegroup is too dense.  It isn't easy to spot an overcharge.  Do yourself a big favor and switch to something that runs cooler and is bulkier.

[9x45]

Stepped case. IMT, Freedom Munitions, AmmoLoad, and MaxxTech. look at pic 4, you can see the ledge. Complete junk. Case rupture or KaBoom waiting to happen, especially in a PCC. 

[Ssanders224]

16 minutes ago, 9x45 said:

Stepped case. IMT, Freedom Munitions, AmmoLoad, and MaxxTech. look at pic 4, you can see the ledge. Complete junk. Case rupture or KaBoom waiting to happen, especially in a PCC. 

 

Nah. 

Thats a CBC (Magtech) case. I’ve never seen a stepped CBC case. 

 

Honestly, everything is pure speculation other than the fact that some 320/X5 chambers are very unsupported.  Could it have been over charged? Sure, that’s possible (although I don’t think that’s the case). Could the projectile have been set back? That’s possible too. Fired slightly out of battery? Case web let go due to being unsupported? Those are possible too. No one will ever know for sure, and responses here are just conjecture. 

 

Id slap a Bar-Sto in it, replace the extractor, and let her rip. 

[Yondering]

Agreed that CBC is not stepped brass, and pic 4 does not show a ledge. 

 

However, only two things can cause that damage to the case head - high pressure, or extreme excess headspace allowing the case head to slam into the breech face (aka 40 S&W in a 10mm chamber). It's extremely unlikely there was enough headspace in any 9mm to do that, so it leaves us with high pressure. That's not conjecture, although speculating on the cause is. 

 

We have signs of high pressure (case head damage and expanded primer pocket), rapid slide unlocking (striker swipe on the primer and case head), and case blowout shape indicating lack of case support. Those are facts we can see in the pics.

 

Conjecture is why those things happened, and we probably can't know without more details. In my experience though, this is probably a combination of high pressure in a gun that unlocks too easily due to light springs. Given that it was a 135gr bullet in a CBC case, it's a pretty safe guess that the bullet base was into the case taper, so it's likely the case was jammed in the chamber without enough room to release the bullet, which definitely causes high pressure spikes. The same load in other brands of brass may be perfectly safe. 

[superdude]

The firing pin hit is dead center on the primer, so you can probably rule out an out-of-battery event. Out-of-battery firing, at least in a Glock, is evident by an firing pin hit off-center on the primer because the barrel has not slid all the way up the breech face and the cartridge is not quite in perfect alignment with the firing pin. 

[Yondering]

51 minutes ago, superdude said:

The firing pin hit is dead center on the primer, so you can probably rule out an out-of-battery event. Out-of-battery firing, at least in a Glock, is evident by an firing pin hit off-center on the primer because the barrel has not slid all the way up the breech face and the cartridge is not quite in perfect alignment with the firing pin. 

 

IME when we talk about out of battery events with striker fired guns, the barrel and slide are almost completely locked up (firing pin/striker is more or less centered) but the slide doesn't quite close all the way forward. That's not actually "out of battery", but does allow the slide and barrel to unlock too early, sometimes causing a blowout. This usually happens when a round just barely chambers far enough to lock up but is tight enough to cause some drag in the system and the slide doesn't have enough oomph to close all the way but gets far enough to trip the striker. The other time this can happen is when the recoil spring is too light for the striker spring in a Glock, and pulling the trigger retracts the slide a little bit but still allows the striker to drop. That's a poorly set up gun problem, but I don't know if it can happen with a 320. 

 

I've never seen a Glock or any other striker fired pistol that would actually fire with the barrel truly "out of battery" as you describe, other than if the slide is hammered forward in a slight incomplete lockup. Test your own guns, retract the slide until the barrel starts to drop out of lockup; if the striker will drop at that point, parts are badly out of spec and need to be repaired, but that is what it would take to cause the off center primer hit "OOB" condition you described. 

 

That's a different thing than a barrel that locks up too high or low, causing an off-center primer hit but normal function.

 

The fact that his firing pin drug all the way through the primer and across the case head tells us the slide unlocked a lot faster than normal, which is a strong indication of an "out of battery" firing (of the type I described above, not what you said). 

Edited September 19, 2019 by Yondering

[superdude]

Here's an example of a Glock firing out of battery https://www.ssusa.org/articles/2018/8/14/firing-out-of-battery/

 

I agree with the firing pin 'wipe' in this example. I've never seen one so extreme as in this case. It certainly looks like the slide must have unlocked super fast. I'm not familiar with the Sigs, so I can't say much one way or the other. I am surprised by the poor case support in these barrels. That looks scary. 

[mikeg1005]

Polish the feed ramp

 

[Yondering]

On 9/19/2019 at 8:35 AM, superdude said:

Here's an example of a Glock firing out of battery https://www.ssusa.org/articles/2018/8/14/firing-out-of-battery/

 

I agree with the firing pin 'wipe' in this example. I've never seen one so extreme as in this case. It certainly looks like the slide must have unlocked super fast. I'm not familiar with the Sigs, so I can't say much one way or the other. I am surprised by the poor case support in these barrels. That looks scary. 

 

Sorry for the delayed reply, I wanted to take time to read that article and consider your points. Long post ahead, I found this hard to explain in fewer words. 

 

I do see the conclusion you made from that article, however, IMO that author is using the wrong terminology and the article is misleading. His pistol was not firing out of battery (the slide was closed all the way forward), he was just forcing reduced locking lug engagement because of loose tolerances. In my opinion a gun that does what he showed is out of spec and should be repaired, but that's a different topic and won't help the OP of this thread. What the author of that article defined as out of battery was not actually out of battery.

 

Apologies in advance if this stuff seems too obvious to you and the OP, just want to be clear:

The important detail about that is the author's Glock slide was closed all the way, and I think the OP's X5 slide in this thread was not. The picture below illustrates what I'm trying to describe; I used a Tanfo because it's the most visually obvious to show the path of the barrel, but the concept is the same for all pistols using the Browning-style recoil operated locked breech system. (sorry for the small text in the pic, thought it would turn out bigger)

 

The "delay" section is that first bit of slide travel as it moves rearward from "in battery"; that distance changes depending on the gun, but lets call it about 1/8". The delay is very important, because as the slide and barrel stay locked together during that travel, it allows time for chamber pressure to drop down to safe levels. There is a smaller range of that "delay" section where the gun can fire; if the slide is too far rearward the firing mechanism is disengaged. That prevents the pistol from firing when the barrel is not locked to the slide, which would be very dangerous. When people say that a gun shouldn't be able to fire out of battery, this is what they're referring to; it's generally correct except during that range of the "delay" zone where the gun can still fire with the slide slightly retracted. 

 

The "unlocking" section is pretty obvious; the barrel drops out of lockup in the slide and stops it's rearward movement. 

 

So, in the article linked above, the author's pistol was at the "in battery" position, but tolerances were loose enough that he was able to push the rear of the barrel down slightly until it contacted the locking block, this allowed offset primer hits. Note that in most pistols, this allowable movement should be very small, and often none at all in carefully fitted guns. In the condition that author simulated, the barrel and slide still followed through the delay section of barrel/slide movement, because the slide was in battery, thus it did not cause an unsafe condition. 

 

In the OP's pictures above though, we see a centered primer hit, but evidence of severe firing pin/striker swipe indicating rapid and early unlocking. I think this tells us that the slide did not go all the way into battery, but stopped somewhere in that "delay" zone, probably just barely far enough to engage the firing mechanism. That would be caused by drag of the barrel or slide against the frame; in this case I think an oversized round kept the barrel from locking completely into the slide, causing drag between the barrel lower lug and frame's locking block. Between that drag and the light weight recoil spring, the slide probably stopped early in the "delay" zone, closer to the unlocking point than it should be. 

That resulted in the barrel unlocking from the slide too early (striker swipe caused by downward barrel movement) while the chamber was still under high pressure. That condition combined with poor chamber support resulted in the kaboom.

 

My takeaways for the OP are:

1 - stop using CBC and Aguila brass with 135gr bullets. The internal taper of CBC brass is too long, and the 135gr bullet seats into it and causes a bulge. That bulge can cause high pressure, and can prevent the gun going into battery. Aguila brass has the same problem with internal taper.

2 - Bump up the recoil spring weight a little, make sure the slide closes completely every time even when very dirty and the pistol is held vertically with the trigger pulled. 

3 - maybe consider an aftermarket barrel with more support. I wouldn't consider that mandatory, but it might be good for peace of mind. 

Hope that helps and makes sense.

 

Edited September 21, 2019 by Yondering

[dillon]

Another possibility is that the cartridge fired just before this one was overcrimped, and left a ring of the bullet plating in the forcing cone. Overcrimping a plated bullet can crack the plated jacket, which remains behind upon firing.  This acts as an obstruction, raising pressure. I've only seen this once, in a S&W 4006. It belonged to a local PD. In this instance, it cracked the barrel and damaged the slide. This was over 25 years ago, and plating technique has greatly improved since then, but still worth pointing out the possibility.

[Jim Watson]

Looks like extremely high pressure from a gross overload.  Chintzy brass maybe a secondary contributor.

What I have read here about Evolution powder measures, I have no problem accepting a double charge.

 

I have been doubtful of the "out of battery excuse".  I see what you are saying about a LITTLE BIT out of battery, but would like to see it experimentally confirmed.

I have a design for a device to induce controlled out of battery slide position.

Now if somebody would just donate a gun to risk... 

Edited September 27, 2019 by Jim Watson

[Yondering]

5 hours ago, Jim Watson said:

I see what you are saying about a LITTLE BIT out of battery, but would like to see it experimentally confirmed.

 

I'm not sure which you need to see confirmed - that most guns will fire a little bit out of battery, or that it can cause a problem? The first one you can verify yourself with an empty gun. The second one should be obvious that reducing the delay time before unlocking results in higher pressure at unlock. Combine that with a high pressure load to start with and there can be a problem. 

[Jim Watson]

I am sure most of us have played with a gun to hear it click with the slide back a bit.

What I would like to see tested is whether it will fire with the slide back 0.xy" and whether that will speed up unlocking to where the case ruptures.

[HesedTech]

On 9/27/2019 at 9:29 AM, Jim Watson said:

Looks like extremely high pressure from a gross overload. 

This^^^
 

I think you all are over analyzing/thinking this. I’ve seen unsupported cartridge discharge (I’m talking not even in a gun) and it by no means had this much damage. 
 

While the gun may not have been fully locked up the damage is far too great for anything other than an over charged cartridge. The gun springs should have nothing to do with it, assuming the barrel was fully locked up.
 

CBC brass is as strong as any other, the cartridge was loaded with TG which could leave room for extra powder, and any  reloading press can double charge if the operator makes a mistake.

 

Good pictures though and they generated a lot of interesting comments. 

[Yondering]

4 hours ago, HesedTech said:

 

I think you all are over analyzing/thinking this.

 

Nah, you're just missing a lot of the evidence in the pics and OP's description. Simple explanations are good, but ignoring evidence and over simplifying is not. Ignoring potential issues like that brass and bullet combination is helpful to nobody, and potentially dangerous to the OP if the same thing happens again. 

 

High pressure alone does not cause the striker swipe that we see on that case, that's a timing issue. I've worked up loads to failure in a number of different guns and have never seen that caused by high pressure by itself. The OP's description indicates more than just a high pressure event too, from my own experience of similar events. 

 

Light springs definitely have an affect on a slide not going all the way into battery; that's the risk with using light springs. Disregard that at your own risk, especially in striker fired guns.

 

The problem with CBC brass has nothing to do with it being strong or weak. It has too much internal taper to use with most 135gr bullets without bulging; that is fact that anyone here can check for themselves. The bulge that bullet and brass combination causes will stick in a lot of 9mm chambers unless they are pretty loose; again something easy to verify, especially for the OP. If the OP ran that round through a Lee FCD and made sure it plunked, then maybe that wasn't the issue, but otherwise it's a pretty likely contributor to the event. 

 

It's also proven fact that a loaded round wedged into a chamber without room to release the bullet causes high pressure. Combine that with the use of TG which has very little room for error. 

 

Taking all of that into consideration, we have multiple indications something other than just high pressure happened, and no indication at all except for high pressure signs that a double charge was the problem. A double charge may have happened, but we don't have anything that points to that specifically instead of some other cause of high pressure.

[chevrofreak]

Maybe they picked up one of my 9major cases and reloaded it?

 

The only case blowout I have ever personally witnessed was with a second loading of an Everglades case that was initially loaded as 9major with HS-6, then loaded with 3.4gr of Titegroup and a 147gr plated bullet.  My girlfriend was at the bench next to me firing my suppressed AR9 pistol and I was peppered with brass when the case blew out.