Some kind of cord hanging from the officer's uniform would be an easy guess. There are several accounts of officers causing ND's when the pull cord from a jacket is tangled in the trigger guard. Using the wrong holster is another possibility. There is a famous account of a Canadian soldier shooting himself with his P320 because he was using a holster for a P226. Let me turn the question around on you: if you loaded a P320 and set it on a shelf, what would cause it to discharge itself? Are we saying the trigger moves on it's own? Is the sear slipping off the striker? These events should be provable and repeatable. The one constant I see in all these ND's is that the weapon is holstered. Can you squeeze, twist, vibrate a holstered P320 until it fails without touching the trigger? Try it. You will be internet famous if you can make it happen.
What us occurring is a combination of factors:
- the slide and frame have some vertical play between them;
- the sear engagement is less than the norm at around .040";
- the parts are MIM and are left unpolished; and
- the firing pin safety is prone to sticking due to powder residue or brass shavings getting stuck.
In order for it to happen, you have to first have the firing pin safety get stuck, and then have the failure between the sear and firing pin.
The people who have replicated it have noted a burr on the firing pin that, as the slide moves up and down in normal use, (holstering, moving slightly in a holster as the user walks, sits, stands, etc.) allows the firing pin to start walking off the sear. The interesting bit is that when it does this, it removes the burr and makes it impossible to replicate with that particular firing pin.
So it's self correcting, after it discharges.
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But you're in good company as Sig is still using the same rationale that you are - blame the user for a negligent discharge due to some type of trigger intrusion. Sig probably did it as it worked extremely well for Glock as a legal defense/liability strategy, because for Glock that was 100% true. And, as noted above when someone is shot or killed by a particular Sig 320, the failure can't be replicated in that particular pistol, so it's a solid legal defense in each and every individual case.
And Sig knows it.
Sig is now filing suit as state training agencies, and local, state and federal agencies are now banning the Sig P320, particularly after the USAF suspended use of the pistol after the fatality at FE Warren AFB where it's clear no one was touching the holstered handgun when it discharged.
They won't make this go away and problem or not, it's reputation is shot, no pun intended.
Sig did address a drop safety issue in 2017 with a voluntary recall. However despite reports of uncommanded discharges as far back as 2016, Sig has done nothing for almost a decade to address these concerns expressed by users. These include over 100 lawsuits with 80 people injured including 33 police officers from 18 different agencies. Sig's only public action on this particular issue has been to blame the user.
A growing number of people and agencies are no longer buying what Sig is selling when it comes to the uncommanded discharge issue.
The issue of when Sig finally realized there was a problem is the wildcard for Sig. If it gets leaked that Sig knew about this issue early on and then pulled a Remington'esque decision to not fix the problem as defending the lawsuits would be cheaper, it won't just be the Sig P320 that loses customer confidence but rather Sig's whole handgun line.
