In our previous examination of Sig Sauer’s P320 uncommanded discharges issue, a whole lot of commenters seem to get hung up on the screw, ignoring the methodology that Wyoming Gun Project laid out in his video. Well, it is a 40 minute video, and maybe he didn’t explain the preconditions for the failure mode he was trying to demonstrate well enough.
Well, here’s a 20 minute video by Shadetree Armorer that explains, in much clearer detail, the part failures the screw simulates before the loose slide come into play.
For legal reasons, he says to add “allegedly” every seven words or so.
“This is meant to be a summary with some connecting tissue uniting the whole so you can understand the big picture.”
“Despite what Sig may publicly claim about the P320, it relies on exactly two things to not go off, and the trigger isn’t one of them.”
“The first thing the P320 relies on is the sear. It is important to note that, unlike a Glock or even a 1911, there is no feature or device that blocks movement of the sear when the trigger is not pressed to the rear.”
“It is floating on two coil springs. These two coil springs and by way of geometry, pressure from the striker spring, are the only thing holding the sear in place.”
“The second thing that the P320 relies on is the safety lock, more commonly referred to as the striker safety or striker safety lever, which is held in place with a torsion spring. So, in order for a SIG P320 to discharge without a trigger pull, both the sear and striker lock must move, and those things are only prevented from moving by spring force.”
“The firing pin safety, that part was designed to be stamped. Someone in finance was like, ‘Hey, let’s save like $30 per pistol.’ So, a bunch of parts that were designed to be stamped end up becoming MIMed [Metal Injection Molded], which includes that striker safety. So, what’s the difference between stamping and MIMD in terms of safety and quality? With MIMing, once in a while, you might run into bubbles in the safety lever. If the bubbles break, then you have a problem where it shears off, the striker goes forwards.”
“With safety levers in particular, if there’s a wear issue, the striker goes forwards and the safety lever saves you a few times. There’s a possibility that it’ll break after a few instances of it happening. Out of the box, if you have a good one, the pistol should be safe, which is why the majority of 320s haven’t gone off. But if you have a bad one out of the factory or if you drop it too many times, then you might have a problem.”
This, by itself, is not enough for an uncommanded discharge. “You also need a sear issue.”
Next up: The FBI Ballistic Research Facilities report on a Michigan State Police P320. Quoting from page 29:
Because of the inherent movement between the slide and frame, a third test of the striker safety lock was conducted. Approximately 50 attempts were made to determine if the striker would impact the prime case after manipulating the weapon while holstered. The weapon was pressed together and pulled apart at the slide and frame. Thereafter, pressure was applied to the frame and the sear manually released from the primary notch. The intent of the manipulation and pressure was to mimic what might occur to a holstered weapon during an officer’s duties, such as running, jumping, climbing, fighting, pressing a weapon against a wall or vehicle, or obtaining a master grip on the pistol prior to drawing, etc.
BRF staff observed the prime case fired on nine attempts, with the primer indent measuring between 019 and 0026 of an inch with, an average of 023. While staging one attempt to allow another BRF staff member to observe the striker safety lock function as designed, the weapon was prepared and placed in the holster with no manipulation. A second staff member released the primary sear notch from the striker and the prime case fired, indicating failure of the striker safety lock.
“The important thing to take away here is that the striker safety in the examined firearm was able to be defeated by simply jostling the P320 in the holster, as would be expected to happen for any firearm carried in the holster throughout the day.”
Following the airman’s death, the Air Force released instructions on checking the striker safety in each gun. “The Air Force does not trust the striker safety lock either. They also mentioned specifically to check for proper assembly.”
“So, we have good reason to believe that the striker safety design is compromised and ineffective. Anecdotally, I have also heard reports elsewhere that it is sometimes assembled incorrectly from the factory, with one leg of the torsion spring being dislodged.
“I have also heard anecdotal reports that fouling such as carbon, unburnt powder and brass shavings can overwhelm the spring, and as a result the safety lever sticks in the upwards defeated position. My perspective on this is that the design seems to allow for a lot of surface area for fouling to build up when compared to the typical round plunger design.”
“There does not seem to be a singular problem with this safety lever. Rather, there are allegedly a lot of problems.”
“Why did SIG choose this design? Well, it is very compact and it saves having to cut a pocket in the slide for a striker safety plunger design like Glock, Smith and Wesson, and pretty much every other striker fired pistol use.”
The P365 doesn’t use safety lever design of the P320.
“The second thing that needs to happen for a P320 to discharge without a trigger pull is that the sear needs to release the striker. Now, you’re never going to guess. It looks like there’s multiple alleged ways for this to happen as well. And they can combine and get worse, just like the striker safety lever issues.”
“First, it seems as though there’s the potential for the takedown lever for large frame guns, that is 10mm and .45ACP, to get mixed up with the takedown lever for small frame guns. Whether this has happened in factory guns has yet to be seen. However, one of the most stalwart defenders of the P320’s honor, Grey Guns, has put out a notice stating that this combination of parts can create an unsafe condition.”
“I won’t get too into the weeds, but the take down lever is what allows the P320 to be disassembled without a trigger press. And it does this by lowering the sear via an arm. For whatever reason, Sig designed the large frame and small frame pre-P320 takedown levers to fit interchangeably. But importantly, the large frame takedown lever reduces the sear engagement in the small frame guns when it is in the assembled and ready to fire position.”
“The second way this can allegedly happen is poor surface finishes, or geometry of the interface between the striker and sear. Because nothing forces the P320 sear to fully engage in the way that the drop safety slot in a Glock trigger housing forces the Glock trigger bar to fully engage the striker, we are again reliant on spring pressure combined with a bit of geometry. However, should the geometry be off or a poor surface finish, or a burr be present in the sliding searsurfaces, these parts can get hung up, resulting in reduced sear engagement.”
“The FBI BRF’s report of the MSP320 that discharged in a holster found that one of the sliding sear surfaces had a ledge. And the US Air Force’s supplemental inspection criteria released on July 22nd specifically calls out the sear and striker assembly as areas to look for damage.”
“The third way that the sear and striker engagement can be reduced is by fouling or debris. That’s a bigger subject that we’re going to get to later because it affects all P320 pistols.”
“The important thing to note is that none of these problems are enough on their own to make the sear release the stiker uncommanded.”
“I was reminded of the Swiss cheese safety model by Gen Y Revolver Guy on Arfcom.” In which only when several problems occur at once, passing through different Swiss cheese holes, does the problem occur when all the holes (flaws) happen to line up. “That final piece of Swiss cheese in this situation, which all the issues I’ve covered combine with, is excessive movement between the slide and frame that seems endemic to the P320 platform. In particular, the slide can move up and down relative to the frame, which is enough to shift the sear engagement. And combined with one or more of the three aforementioned issues of incorrect takedown levers, bad sear surfaces, or firing debris, this can be enough for the sear to let go of the striker entirely.”
Now the part most immediately relevant to this previous post. “In these videos from Wyoming Gun Project, the loose slide to frame fit is demonstrated as well as the ability for that slide movement to release the striker when the striker engagement is reduced. It’s important to note that he set his P320 up to have reduced striker engagement by using a screw to pull the trigger to the rear a small amount past the wall in the travel after the takeup. And the takeup also serves to defeat the striker safety lever. So those two issues are simulated here while the third issue loose slide to frame fit is demonstrated.” Those who still don’t understand the purpose of the screw should read and reread that section until they do understand.
“It’s not simulating a screw getting stuck in the trigger. It’s a static and repeatable simulation of other known issues.”
Back to the debris issue. “The design of the P320 seems particularly susceptible to capturing environmental debris between the sear slide and striker. Indeed, these parts all combine to form a pocket. And if the pistol is carried muzzled down in a holster, the bottom of that pocket is a place where fouling and debris can accumulate.”
“Worse, there’s a gap between the frame and the slide directly above that pocket through which things from the environment can fall into.”
“This video from YouTuber Mischief Machine demonstrates that if the area is fouled with unburnt powder and brass shavings, the sear engagement can be reduced to the point that the slide movement will release the striker.”
Once Mischief Machine inserts the debris with the strike safety already simulated off, he gets the gun to discharge by tugging on the slide.
Again, the P365 doesn’t suffer from this P320 design flaw.
“I think that tidies up things nicely for this P320 saga. It’s pretty obvious what the problems are. The FBI and the US Air Force both seem to be on the same trail, and I honestly don’t think SIG has a realistic chance of fixing all the problems.”
“I think their only option at this point may be bankruptcy, which is why they are pushing so hard with the PR spin to gaslight everyone.”
Shadetree Armorer also points to YouTuber Dick Fairburn’s SIG P320 An unfolding Disaster, which I haven’t had a chance to watch yet (it’s another 40 minute video, and seems heavy on talk and light on illustrations).
I had no intention of doing another Sig P320 post so soon after the last one, but the video was so informative on the (alleged) flaws, and so clear on things people seem to be getting hung up on, that I thought it was worth posting.
