Some of you may know about this incident. I only learned about it in any detail recently.

In 2002, Officer Jesse Paderez of the San Fernando Police Department was killed when his P220 discharged after falling off of a stack of documents he was carrying. The pistol landed hammer-first on the ground.

I just watched an interesting video by Massad Ayoob about the rise and fall of the use of DA/SA pistols in law enforcement. In one section of the video, Mas mentions that manually decocking the hammer (instead of using the decocking lever) deactivates the firing pin block. This is of course true for all of these guns (otherwise they wouldn't be able to fire), but his implication was that in some of the designs, manually decocking the hammer deactivates the firing pin block "permanently" (or at least until the next firing/loading/unloading cycle has been completed). He then goes on to talk about Jesse Paderez's story as being an example of this phenomenon, and that it was the reason why his P220 killed him.

However, there's a problem here. Even if you manually decock a DA/SA P-series, the firing pin block will push back down on the internal safety tab (that engages it when the trigger is pulled) as soon as the trigger is released. This is because the firing pin block is under spring tension, whereas the internal safety tab is not. To the best of my knowledge, the above is true of any properly functioning DA/SA P-series pistol since they debuted in 1975 with the P220. In other words, I think Mas is mistaken and that Officer Paderez's pistol must have had some other issue.

I figured this forum would maybe have someone who can shed some light. Was the real issue with Officer Paderez's pistol ever determined?

For those interested in Mas's video, here you go:

I don't know about the Paderez case, but I do know that early P220's with the spur hammer did not have the hammer pull back spring and clockwork like the newer models. If you decocked the older style hammer manually with the thumb (not using decock lever), the hammer would stay sitting against rear of firing pin. Now normally there is still a firing pin block, but the firing pin block isn't a comparatively large piece of metal (say compared to the much larger lockwork of the hammer) and I could see enough impact force breaking past the firing pin stop, especially if it's worn.

So for example, with a more modern P220, the hammer is automatically pulled backwards by a spring after being manually thumb or decock lever dropped, the hammer is pulled backwards and then locked away from the firing pin by the large engagement surfaces of the hammer/sear. The larger engagement surface would take a much larger force to shear this hammer safety from a drop on the hammer.

With the old style spur hammer manually thumb dropped onto the firing pin, any impact on the hammer transfers directly to firing pin and the correspondingly much smaller firing pin block. On the old style spur hammer, a decock lever hammer drop, would leave the hammer sitting on a safety ledge which should take a drop impact just fine. It's only when you manually drop the old style hammer you lose the impact safety of the hammer.

Thanks for that. I was also considering that possibility. I don’t think my knowledge of physics is as good as yours, but in your proposed scenario, I’m assuming this is the logic:

Pistol dropped hammer-first while at half-cock position (i.e. resting on safety intercept notch):
The force of impact when hitting the ground must be great enough to a) force the hammer past the sear notch, b) have the hammer strike the firing pin hard enough to force it past the firing pin block and c) have the struck firing pin hit the primer hard enough to detonate it. A fall from chest height likely would not generate sufficient force to complete all three steps - a, b, c - and in fact, may fail to complete any of them.

Pistol dropped hammer-first while at full-forward position (i.e. resting on firing pin):
The force of impact when hitting the ground must only be great enough to force the firing pin past the firing pin block and have sufficient kinetic energy remaining for the firing pin to detonate a primer, in this instance, the hammer itself acting as nothing more than the middle sphere(s) in Newton's Cradle. A fall from chest height might be sufficient to accomplish this.

My terminology may be off, but is that what you’re getting at?

Yes, exactly!

^^^Thank you. I did some more digging and found this thread on another forum.

I did some testing on my own. The thread I linked above has several posts that maintain that on an "older" P220, which likely just means a P220 without the rebounding hammer (as Xer0 had mentioned), manual/thumb decocking will defeat the firing pin block. In other words, the posts in that thread concur with Mas Ayoob.

I don't own an older P220 (haven't in a long time), so for the test, I used a P228 (i.e. a folded slide SIG) and a P229 (i.e. a milled slide SIG). The reason I chose both was just to see if anything changed in the way the firing pin block functions (folded slides and milled slides do use different firing pin blocks).

Anyway, my theory (playing devil's advocate) was hinging on the simple fact that when the hammer is all the way forward (possible on an older P220, but not on any other P-series, as they all have rebounding hammers), the firing pin cannot return all the way to rear, as it needs to protrude slightly into the space now being occupied by the hammer, in its at-rest position. Because of this, perhaps the firing pin block is unable to re-engage, as the cutout in the firing pin hasn't reached quite reached it yet.

The test for this was easy. I just removed the slides of the pistols I had on hand (the P229 and the P228) and manipulated the firing pin and firing pin block manually. The above theory above didn't pan out though. The rear of the firing pin (where the hammer strikes it) is still below the surface of the slide (i.e. recessed in the hole at the back of the slide) when the firing pin block re-engages. This is true for the folded slide and the milled slide. In other words, the hammer resting firmly on the back of the slide doesn't, on its own, prevent the firing pin from returning far enough for the firing pin block to re-engage the cutout in it.

This leaves only one possibility that I can think of, which I cannot test for readily, and it's that SIG redesigned the firing pin block when they switched to the rebounding hammer. To the best of my knowledge though, this is not so (hasn't the firing pin block for all folded slides always been the same?). Maybe one of you with an older P220 (non-rebounding hammer) can do the test I did above.

Moving on, for anyone who also thinks of it, my other devil's advocate theory was that the non-rebounding hammer, when in the full forward position, tensions the trigger bar by pulling back on its DA arm slightly, causing the internal safety lever to raise, thereby disengaging the firing pin block. This is another theory that's easily tested, and it also doesn't pan out. The internal safety lever does not raise until the trigger is close to the end of its travel, when executing a DA pull. Is it possible that the old P220 is different in this way? Maybe it is, but I highly doubt it; when executing a DA pull, the internal safety lever raises when the trigger shoe is where it would be in SA - if it raised before that point in the trigger shoe's travel, the firing pin block would only be defeatable in DA mode.

In short, Mas appears to still be incorrect given the above. However, the test conducted by the most prominent poster in the thread I linked is pretty damning. He simply chambered a primed case in his old (non-rebounding hammer) P220, manually decocked the hammer, struck the rear of the hammer with a rubber mallet, and it went bang.



Perhaps the firing pin block is only strong enough to prevent the firing pin from moving only when the firing pin is just bouncing around under its own weight? Direct impact to the firing pin by another mass makes it easily skip past the firing pin block? Xer0, you may be right!