Sig P320 "Uncommanded Discharges" (Merged Threads)

OK... let's see if this makes any sense. I don't own a Sig, so pardon my use of my EDC P80 for demonstration purposes.

The trigger pocket / cover in a holster has an indentation (yellow outline) on both sides that traces the inside edge of the trigger guard. If that indentation is deeper than it needs to be to create a retentive friction point on the gun's trigger guard, it could conceivably put some rearward friction on the trigger itself as the gun is inserted into the holster, right? Perhaps not enough to push the trigger all the way back. But enough to move it... say... a millimeter or two rearward... and hold it there. (continued below the photo)
Sig-demo-2.jpg


Then, additional jostling or vibrations may nudge the slide enough to disengage the barely-hanging-on sear, allowing the firing pin to fire.

Here's a diagram I made of the top view of the holster. Again, yellow part is indented part of the holster trigger pocket.

Sig-demo-1.jpg


This is how I imagine a potential "uncommanded discharge" happening. The culprit is "out of plain sight."

It could happen.gif
 
Yes, there are situations that can absolutely make a Glock behave similarly to the 320. The 320 trigger seems to be on the ragged edge for a duty gun based on the tests I’ve seen. I’ve got a few range guns that have very limited pretravel and any additional rearward movement will start moving the sear down the lug. Now, the difference I see is that most Glock based guns are not as loose as the 320 and that looseness is what looks to be causing the disengagement of the sear but the 320’s secondary safety is not stopping the firing pin. The Glock firing pin safety will unless the firing pin safety is fully depressed. Now, I’ve seen some intentionally trying to get the trigger below 2.5lbs and the only way to do that on the DA models is to eliminate so much pre-travel that the VE is depressing the firing pin safety and the sear is hanging by a thread which as we all know is not safe.
 
My little "illustration" wasn't intended to compare Glocks to Sigs. I don't have a Sig, and the Glock was just a "model" gun. It could have just as well been a "blue gun."

I'm just trying to demonstrate how a holster could exert some rearward pressure on the trigger (of any gun for that matter). But combine just enough pressure to pre-stage the trigger AND a sear engagement so precarious that a loose slide could move enough to nudge it "off the ledge" and cause it to fire.
 
Racer88 said:
My little "illustration" wasn't intended to compare Glocks to Sigs. I don't have a Sig, and the Glock was just a "model" gun. It could have just as well been a "blue gun."

I'm just trying to demonstrate how a holster could exert some rearward pressure on the trigger (of any gun for that matter). But combine just enough pressure to pre-stage the trigger AND a sear engagement so precarious that a loose slide could move enough to nudge it "off the ledge" and cause it to fire.
Click to expand...
Oh, I get it and completely understand.
 
What you need if your buddy owns a Sig..

1754344636921.png
 
bkbrno said:
The fact that SIG removed that leg of the sear from a later design should make you think a little. I have no idea what removing that leg actually does to the overall design of the system. It may cause more problems than it solves.
Click to expand...

Looking back on this, I think you are right on the money here.

While the stated goal of the "Voluntary Upgrade" was a weight loss program to address drop-safe concerns, Sig made a bunch of other changes to at the same time. The extra leg added to the back of the sear could double as a disconnector if all the parts are in spec. And in practice, most of the P320's with extra leg do work that way (a failure of the sear engaging the striker hook pushes the sear down, and that extra leg pushes the trigger bar down and out like a disconnector would.) This hasn't effected every post-upgrade P320 because the engagement angles on the striker and sear normally pull the two parts towards each other and render all of this un-necessary.

Thing is, Sig also played with a seperate disconnector that uses the slide to push the trigger bar down when the slide is out of battery.... they implemented two solutions to the same problem and created a new problem in some assemblies as a result. As someone with some engineering background, I can see how that happens... you get fixated on solving a problem, come up with a successful solution, and only later realize you created a new set of conditions where the new design fails. It is a real "Oh Shit" moment. Possibly career ending.

Normally, I would have some sympathy for the engineers at Sig. Dumb shit happens all the time and you go back to your desk and try again. We are all human. However, the sheer arrogant duche-baggery Sig management exhibited over this has exhausted any good will I have for them. They created one hell of a mess and if they get burned down over it, well, they earned every second of it.

Fixing the mechanism is going to be a painful process of going through every P320 that has been manufactured to correct the few that exhibit this potential problem of bad sear engagement coupled with disabling the striker safety. It would be cheaper to just recall all the FCU's en-masse, throw the parts in the trash, install new redesigned parts, then test the function of the FCU before returning the pistol to the end-user. It is a manufacturers worst nightmare. But it could be done.

Fixing the damage done to their reputation. Well... Good Luck to that. I wouldn't trust them to build a tricycle at this point.
 
On a separate note, the proposed redesigned sear/manual safety put forth in the patent application of Brian McDonald (or Angled Spade) looks quite feasible. Altering the shaft of the manual safety lever to have a notch that mates to a surface on the sear looks good. It would lock the sear in place when the safety lever is set, or allow it to move when the manual safety was off. Only takes two new parts to implement if the FCU is already cut for manual safety levers.

It does change some procedures the end user must do when working the pistol. For example, with the sear physically locked in the up position, you would absolutely have to set the safety into the fire position any time you need to move the slide. That could be a good thing, but it will likely cause training issues if the users is used to leaving the safety in the on position when racking the slide to chamber a round. Same thing if the user needs to clear the pistol. You would have to set the safety to the fire position before you clear a chambered round, otherwise the slide will get bound up on the top of the sear when you pull the slide back.
 
Last edited:
Racer88 said:
This is how I imagine a potential "uncommanded discharge" happening. The culprit is "out of plain sight."
Click to expand...

Yup. This is one scenario that would effect any holstered firearm. The lever built into the Glock trigger is expressly designed to mitigate this potential risk. Sig's don't have that feature.

Also, the force required is higher, since the trigger pull of the Glock mechanism has to add the extra energy into the striker spring needed to ignite the cartridge primer. The Sig has 100% of the energy stored in the striker spring before the trigger pull even begins. The whole trigger function of the Sig is to unlock the striker during the takeup, then release all the energy of the striker. So the Glock design is inherently safer at rest or in a holster... even if something manages to get into the trigger guard, but at the cost of a heavier trigger pull.
 
I honestly have NO idea how the Sig 320 firing mechanism works. I've never seen one, and haven't seen any videos demonstrating it (like the famous "How a Glock Works" video). Accordingly, all the comments above describing what would and wouldn't work are "Chinese" to me. No clue what you guys are talking about.

But I really don't need to know how it works, and I am puzzled. Here's why.... Safe pistol firing mechanisms that WORK have been around for literally a century. Why on EARTH are they having a problem with this one? Why reinvent the wheel?? Is it because it's a "modular" firing control unit that can be swapped out to different grips? Did that force the reinvention of the wheel?

How about they just use the firing mechanism that has worked for a century??? You know the one that is proven safe and WORKS??? I simply don't get it.

Oh... I've said it before... Sig should have done like Tylenol did in 1982 and recall ALL of the product IMMEDIATELY. Take them all back and refund all the money. No conditions. Just fucking do it. It is the ONLY answer to save their reputation and future viability of the company. Even Sig fan bois are saying,"I'm out." Even the ones who don't own a 320! Sig has stepped HARD on their own dick in a STUNNING way.
 
Last edited:
A little something anybody with a P320 should have in the tool box. A cut down slide end plate

P320_Dust_Cover.jpg


Mill off the extension that covers the sear, install it on the slide, and you can visually see the striker/sear engagement, just like the Glock Armorers End plate. I wouldn't leave it on a carry gun for obvious reasons, but on a range gun it is worthwhile to check sear engagement while the pistol is being shot to see if those mating surfaces are pulling themselves towards each other as they are supposed to .
 
Racer88 said:
But I really don't need to know how it works, and I am puzzled. Here's why.... Safe pistol firing mechanisms that WORK have been around for literally a century. Why on EARTH are they having a problem with this one? Why reinvent the wheel?? Is it because it's a "modular" firing control unit that can be swapped out to different grips? Did that force the reinvention of the wheel?
Click to expand...

The answer to this is so simple. The P320 is Sig-Sauer's first attempt at building a striker fired handgun. Every handgun they ever made before this was hammer fired.

Now, they used a proven design.... a fully compressed spring around a striker. The same mechanism that is in nearly every bolt-action rifle since Mauser came up with the idea in the late 1800's. All the energy needed to fire the cartridge in on tap the second you close the bolt. The trigger does nothing more than trip the lock and let it loose.

But they blew it due to a lack of experience. What works in a rifle doesn't work so well in a handgun where the bolt (a.k.a the slide) reciprocates on rails. Takes some more effort to safely retain all that energy in the striker, all the time, and only release it when you want it. Glock solved that problem simply by not loading the striker with all that energy until you pull the trigger. Other companies built more robust blocks to keep a wayward striker away from the cartridge.

Seems so stupid, but that's how most engineering failure look in hindsight.
 
clm2112 said:
The answer to this is so simple. The P320 is Sig-Sauer's first attempt at building a striker fired handgun. Every handgun they ever made before this was hammer fired.

Now, they used a proven design.... a fully compressed spring around a striker. The same mechanism that is in nearly every bolt-action rifle since Mauser came up with the idea in the late 1800's. All the energy needed to fire the cartridge in on tap the second you close the bolt. The trigger does nothing more than trip the lock and let it loose.

But they blew it due to a lack of experience. What works in a rifle doesn't work so well in a handgun where the bolt (a.k.a the slide) reciprocates on rails. Takes some more effort to safely retain all that energy in the striker, all the time, and only release it when you want it. Glock solved that problem simply by not loading the striker with all that energy until you pull the trigger. Other companies built more robust blocks to keep a wayward striker away from the cartridge.

Seems so stupid, but that's how most engineering failure look in hindsight.
Click to expand...
Except the GPT and it is fully loaded. A standard Glock trigger is more than 80% loaded and would fire if the sear fell and firing pin safety failed. The likelihood of those two events occurring are probably just about zero. The Glock design is better in every regard and even has a dingus that would have probably prevented most of the discharges from happening.
 
clm2112 said:
The P320 is Sig-Sauer's first attempt at building a striker fired handgun. Every handgun they ever made before this was hammer fired.
Click to expand...
Could they not copy a design that is proven safe and is no longer protected by patents??? File that under, DUH! Why reinvent the wheel?

clm2112 said:
What works in a rifle doesn't work so well in a handgun where the bolt (a.k.a the slide) reciprocates on rails. Takes some more effort to safely retain all that energy in the striker, all the time, and only release it when you want it.
Click to expand...
See above.

clm2112 said:
Seems so stupid, but that's how most engineering failure look in hindsight.
Click to expand...
A very very VERY stupid company in every regard. Holy crap. Corporate suicide.
 
FrankenGlock said:
Except the GPT and it is fully loaded. A standard Glock trigger is more than 80% loaded and would fire if the sear fell and firing pin safety failed. The likelihood of those two events occurring are probably just about zero. The Glock design is better in every regard and even has a dingus that would have probably prevented most of the discharges from happening.
Click to expand...

Yeah, the Glock is a truly remarkable design. To get so much right on the first try, with no prior experience in firearms manufacture, is just one of those stories that get into engineering textbooks.

Meanwhile... Sig, with some of the best hammer-fired guns in the world, blew it so badly... probably also going to end up in the engineering textbooks for all the wrong reasons.

If I were to speculate on what happened I would say it happened like this:

"Hey, The Army want a new gun, but it has to be a striker fired design. It would really help keep the company afloat if we could win that contract by any means. Oh, by the way, we don't have a lot of time to pull it off. So get on it."

Engineers look at the P250...which already is in production, but not selling well... "Well....ummm.... We could gin up some kind of striker firing mechanism to fit inside of this thing. Hmm... a lot of the tooling is already in place to make it... yeah, this could work."

And thus the problem was born. As I demonstrated just now in a different thread, converting a P320 FCU into a P250 FCU is a relaxing bit of part swapping. The two designs share so much in common. I'll bet money that with a little machining and one custom made piece, I could convert a P320 slide into a slide that would work on a hammer-fired P250... they are that close.

So, yeah, I can see how the P320 got screwed up from the start. The need to re-use so much of the P250's basic design limits what you could do to convert it into a striker-fired gun. Mistakes got made and as they say "You don't know what you don't know."
 
I don't know if this is true. But if it is... hoo-boy.

1754685132109.png
 
Read that. Seems somewhat telling that the military is about to ditch the Sig and go with Glock.
 
How many millions (billions?) of our dollars were wasted on the Sig military contracts?
 
Racer88 said:
How many millions (billions?) of our dollars were wasted on the Sig military contracts?
Click to expand...
They may have a clause that will force Sig to take them back if they deem as defective. Military contracts can be thousands of pages long with their forms and your responses and documentation. The process can take many months to complete and are typically very one sided benefiting the military.
 
Back
Top