A question that I’ve long pondered is the purpose of the “safety” tab or blade in the middle of Glock triggers and similar features of other guns, such as the hinged S&W M&P trigger.

The Glock tab would prevent pressing the trigger back to fire the gun if pressure were applied only to the edge of the trigger and did not depress the center tab. A hinged section that could be rotated with pressure on the edge, like the S&W feature, would not, however, serve that purpose.

Because such antirotation features would not be very effective in actually preventing the triggers from being pressed unintentionally, I have always thought that their actual intended purpose, including the center Glock tab, was probably to prevent inertia from acting on the trigger and causing it to rotate and fire the gun if the gun were dropped from a high distance. In another current thread it was pointed out that as part of the SIG P320 “upgrade” to prevent the gun from firing if dropped at a certain angle, the trigger was lightened by removing material from the bow. Because that part of the trigger weighs less, inertia would have less effect and be less likely to cause the trigger to rotate and cause a discharge. (Most of us should know that the trigger modification wasn’t the only thing that the upgrade changed, but that’s what this discussion is about.)

In thinking about and analyzing the issue, however, it recently occurred to me that a discharge due to inertia-caused rotation of the trigger in the P320 was very unlikely to be possible regardless of how far the pistol was dropped. The curved trigger supplied with the pistol upgrade is shown below. As indicated by the balance line, the mass of the trigger is distributed fairly equally above and below the pivot point; I estimate that no more than 60% of the total mass is concentrated below the pivot. The entire trigger weighs 10.6 grams, so the lower part weighs what—maybe 6-7 grams? Furthermore, the upper part of the trigger is attached to the trigger bar which is a substantial part itself. All that means that if the gun were dropped on the rear of the slide, more mass inertia would be acting to keep the trigger in its normal rest position than was working to cause the trigger to rotate to fire the gun.

Other pistols of course have different triggers. More of the Glock trigger mass is located below the pivot point, but there’s still that trigger bar whose mass and inertia if the gun were dropped would be acting to keep the trigger from rotating to fire the gun even without the safety tab.

So, that’s my analysis and opinion. What say the mechanical engineers or other authorities? What’s wrong with my thinking?





* Credit to member monoblok for the term “inertia block.”

Whatever you might think, it happened. And with the recal...er... voluntary upgrade, SIG acknowledged the issue.

Before the issue with the P320, I was skeptical of the utility of the trigger tab/hinged trigger safeties on striker guns. But the P320's inertial firing problems made me a believer.

quote:

Originally posted by BBMW:
Whatever you might think, it happened.

Okay, what happened?
Were the discharges due to something that happened with the rotation of the trigger due to inertia, or something that happened in the striker/sear mechanism?

If it was simply due to the lack of a trigger inertia block (which the P320 still does not have), why all the rest of the modification?

I believe you do not understand my point and question.

As another question for the engineers, how far would the pistol have to be dropped to accelerate 7 grams of trigger weight to overcome the resistance of a 2800+ grams trigger pull weight, even without the counteracting inertia of the upper part of the trigger and the trigger bar?

The low mass trigger was not the main focus of the "upgrade," nor was trigger mass ever identified as the cause of discharges when the rear of the slide was struck with a surface or hammer.

The value of a trigger safety may lie more in perception and inference of due diligence, rather than an actual safety. Moreover, there's a big difference between the P320's fully cocked state, and the Glock's half-cocked state. There are also patent issues associated with the trigger safety, or have been, to say nothing of product signature and recognition.

While a reduced mass trigger may not be the contributing factor to unintentional discharges, reducing the mass certainly can't hurt, with respect to reducing any trigger effect. A stamped trigger or reduced mass trigger may also be less expensive. If one looks to the P320 trigger as the primary focus of the upgrade, one misses the changes and purpose of the upgrade entirely. It's simply the most visible external feature. Everything else took place inside, both in the FCU, and the slide.

A trigger safety bar such as on the Glock may work more to prevent the chances of a tight trigger guard area of a holster from snagging the trigger and causing movement during reholstering, than anything else.

On my personal carry glocks, I use a tau development "glock gadget" striker control device in place of the rear plate on the slide, which enables me to prevent striker motion when reholstering, by pressing on the rear plate. The trigger and associated bar and components can't move so long as I put thumb pressure on that plate.

The Glock trigger tab was intended to prevent inertial firing. Whether or not that was an actual possibility given the mechanics of the Glock action is secondary to the design criteria that the gun will not fire, ever, unless the trigger is deliberately pulled completely to the rear of the trigger guard.

The tangential benefit that some glancing contact with the side of the trigger vs. the face is very minor, and doesn't exist on the S&W M&P design. The number of Glock ND's caused by windbreaker string pulls and bad holster designs (thumb straps or soft leather) are enough to say this benefit is indeed minor.

However, the "Glock-safety" has been interpreted to be a "manual safety" in some states like Massachusetts, that require a manual safety, even though it is decidedly NOT a manual safety. It makes no sense to have a manual safety that is automatically defeated during the normal process of pulling the trigger. This makes it easier to sell Glocks and similar handguns in these states, wheres the P320 and P365 require a true manual safety lever. The long but smooth DAO on a Kahr needs an external safety in its home state of MA but a Glock does not. The Kahr trigger IMO is inherently as safe as a DA revolver.

And now because of customer expectations, LE departmental rules, and other misplaced "safety" ideas, triggers tabs are now pretty much standard on striker fired pistols.

Passive safeties like firing pin blocks and rebounding hammers are there to prevent drop, impact, or inertial firing. Half cock notches are there to prevent the hammer from striking the firing pin if the sear or hammer interface fails. Half cock is redundant to a firing pin block, but half cock came first.

This message has been edited. Last edited by: Lefty Sig,

quote:

A trigger safety bar such as on the Glock may work more to prevent the chances of a tight trigger guard area of a holster from snagging the trigger and causing movement during reholstering, than anything else.

This I think is the cause of ND's on holstered P320's. The trigger is not a whole lot narrower than the trigger guard, and aggressive indentations in a kydex holster that function to "lock" the gun in the holster by the trigger guard *may* be an issue. Glock trigger guards are wider relative to the trigger and offer more "meat" for a kydex holster to grab without encroaching on the trigger.

A while back (before the P320 had it's drop discharge issues, and maybe before the P320 at all) I brought up the issue of the relevance of the trigger tab safety. I mentioned some of the same things you did, mainly that anything that would pull the trigger besides the shooters finger, would likely release the tab safety also. What I got back was that the tab was there in case the gun got dropped, and the trigger was pulled by inertia. I kind of scoffed at that idea.

Then later the P320, which doesn't have any kind of inertia block safety started having drop fire issues.

I can't say I know what the recal...er...voluntary upgrade actually changes. Knowing that would tell us what SIG thought the problem was.

quote:

Originally posted by sigfreund:

quote:

Originally posted by BBMW:
Whatever you might think, it happened.

Okay, what happened?
Were the discharges due to something that happened with the rotation of the trigger due to inertia, or something that happened in the striker/sear mechanism?

If it was simply due to the lack of a trigger inertia block (which the P320 still does not have), why all the rest of the modification?

I believe you do not understand my point and question.

As another question for the engineers, how far would the pistol have to be dropped to accelerate 7 grams of trigger weight to overcome the resistance of a 2800+ grams trigger pull weight, even without the counteracting inertia of the upper part of the trigger and the trigger bar?

I would take the Glock version of the story at face value.
They make a very large percentage of the handguns sold and don't seem to have any credible claims of AD's from dropped guns.

Not any more. They used to.

The P320 hasn't been around as long as Glocks, but don't kid yourself. Glock had plenty of teething problems, too.

quote:

Originally posted by BBMW:
I can't say I know what the recal...er...voluntary upgrade actually changes. Knowing that would tell us what SIG thought the problem was.

It's not exactly a secret.

quote:

Originally posted by sns3guppy:
The low mass trigger was not the main focus of the "upgrade," nor was trigger mass ever identified as the cause of discharges when the rear of the slide was struck with a surface or hammer.

The value of a trigger safety may lie more in perception and inference of due diligence, rather than an actual safety. Moreover, there's a big difference between the P320's fully cocked state, and the Glock's half-cocked state. There are also patent issues associated with the trigger safety, or have been, to say nothing of product signature and recognition.

While a reduced mass trigger may not be the contributing factor to unintentional discharges, reducing the mass certainly can't hurt, with respect to reducing any trigger effect. A stamped trigger or reduced mass trigger may also be less expensive. If one looks to the P320 trigger as the primary focus of the upgrade, one misses the changes and purpose of the upgrade entirely. It's simply the most visible external feature. Everything else took place inside, both in the FCU, and the slide.

A trigger safety bar such as on the Glock may work more to prevent the chances of a tight trigger guard area of a holster from snagging the trigger and causing movement during reholstering, than anything else.

On my personal carry glocks, I use a tau development "glock gadget" striker control device in place of the rear plate on the slide, which enables me to prevent striker motion when reholstering, by pressing on the rear plate. The trigger and associated bar and components can't move so long as I put thumb pressure on that plate.

For those of s trying to follow this what is the practical difference between 320s full cock and Glock half cock?

Everyone seems to have an opinion about what the glock trigger safey tab is for, and until recently, all these opinions were wrong. This is especially true among "Youtube gun expert idiots" calling it "the dingus" and talking about fingers and holsters bushing against the side of the trigger and the "dingus" prevents a discharge.

Gaston Glock himself was asked in a print interview many many years ago "exactly what is the purpose of that little trigger tab?" His answer was "inertia safety to keep the gun from firing if dropped on back of gun - trigger tab has less inertia than the hinged trigger and trigger bar which are free to move" I am paraphrasing of course, but if you find the interview you will see its from a long time ago and most internet gun experts should have know this by now.

If I offended anyone, my apologies - Merry Christmas to all !!!

Its so Glock can say they have a three stage trigger- Take that, Geissele!

I did a quick search, but couldn't find the details.

quote:

Originally posted by sns3guppy:
Not any more. They used to.

The P320 hasn't been around as long as Glocks, but don't kid yourself. Glock had plenty of teething problems, too.

quote:

Originally posted by BBMW:
I can't say I know what the recal...er...voluntary upgrade actually changes. Knowing that would tell us what SIG thought the problem was.

It's not exactly a secret.

quote:

Originally posted by sigmon:
Gaston Glock ....

Thanks for that.

As I mentioned elsewhere, because its trigger pivot point is higher than that of the P320, I could see how inertia firing might be more possible with the Glock. It still seems unlikely to me based on my limited knowledge of the gun, but the Europeans in general seem to be more concerned about such things. And because the trigger safety blade is such an iconic feature of the Glock, it’s not surprising that, necessary or not, its many imitators would adopt it as well. Now I’m wondering if anyone has removed the inhibitor tab from the Glock trigger and experimented to see if the gun could be made to fire by dropping it without the feature.

In any event, I’m glad that SIG evidently recognized that it was unnecessary with the P320. I am still interested, though, in the answer to my question about the mass of the trigger bow overcoming the resistance of the trigger pull weight.

As mentioned, it would be good to know what holsters were supposedly involved with the incidents being claimed against the P320, but keeping in mind that some supposedly didn’t have anything to do with the gun’s being holstered or even handled. As I recall, the guns were just going off by themselves without any human intervention.

This message has been edited. Last edited by: sigfreund,

The purpose of the Glock trigger safety would have been disclosed in the patent of the device, if someone was so inclined to take the time to look it up. Patents are public domain documents.

quote:

Originally posted by sns3guppy:
I use a tau development "glock gadget" striker control device in place of the rear plate on the slide, which enables me to prevent striker motion when reholstering, by pressing on the rear plate. The trigger and associated bar and components can't move so long as I put thumb pressure on that plate.

I am also a fan...

quote:

Originally posted by sns3guppy:
Glock had plenty of teething problems, too.

But, that gives you no call to QUESTION "PERFECTION" !

Any striker fired pistol has to have a sear that holds the striker back when partially (Glock) or fully (P320) cocked. This means that any slide to frame "play" has to be accounted for in the sear/striker interface to prevent any chance of the striker slipping off the sear and moving forward.

Seeing videos of P320's firing by being struck on the back with a hammer implied to me that the impact force was flexing the slide/receiver interface and allowing the striker to slip off the sear and move forward. Now, in this case the firing pin block should still have prevented the round from firing. I don't have pre-upgrade P320 to look at to see how the firing pin block could also have been deactivated by the hammer impact. Inertial retraction of the FPB tab seems unlikely.

Remember that Glock was developed at a time when DA/SA Semi Autos were preferred in LE and Military and SAO had fallen out of favor. To be be classified as DA or DAO, the striker could not be fully cocked and had to be only partially cocked so that the pull of the trigger completed the cocking and then fired the round. A side benefit of this is that the striker only being partially cocked results in insufficient force to ignite a primer even if the striker slips past the sear and the FPB is somehow retracted. Belt, Suspenders, and Bungee Cords.

The XD with fully cocked striker was initially not permitted in DA/DAO competition classes because it was really SAO putting it with the 1911's. Since then "DAO-ish" SAO striker pistols that have a trigger pull that feels similar to a Glock are considered to be equivalent to a Glock and allowed in the same competitive classes.

quote:

Originally posted by sigfreund:

quote:

Originally posted by sigmon:
Gaston Glock ....

Thanks for that.

As I mentioned elsewhere, because its trigger pivot point is higher than that of the P320, I could see how inertia firing might be more possible with the Glock. It still seems unlikely to me based on my limited knowledge of the gun, but the Europeans in general seem to be more concerned about such things. And because the trigger safety blade is such an iconic feature of the Glock, it’s not surprising that, necessary or not, its many imitators would adopt it as well. Now I’m wondering if anyone has removed the inhibitor tab from the Glock trigger and experimented to see if the gun could be made to fire by dropping it without the feature.

In any event, I’m glad that SIG evidently recognized that it was unnecessary with the P320. I am still interested, though, in the answer to my question about the mass of the trigger bow overcoming the resistance of the trigger pull weight.

As mentioned, it would be good to know what holsters were supposedly involved with the incidents being claimed against the P320, but keeping in mind that some supposedly didn’t have anything to do with the gun’s being holstered or even handled. As I recall, the guns were just going off by themselves without any human intervention.

I wonder if it is needed because the trigger spring in a Glock pulls the trigger to the rear. The recoil spring and firing pin spring are pushing it forward. I would suppose that if you had a new/strong trigger spring and a weak firing pin spring there may be a concern of an AD if you dropped it without the trigger tab.

quote:

Originally posted by VictorLouis:
[
But, that gives you no call to QUESTION "PERFECTION" !

I'm actually wearing a "glock perfection" t-shirt, though I certainly don't see perfection in Glock. I do see a very successful utility tool, and I own a number of them, and carry them. To me, Glock is a compromise, and much as I don't want to like them, I do. More importantly to me, I trust them, despite their imperfections. There's nothing particularly refined about a Glock and they're not precision tools. Just effective ones that do a good job. When I say non precision, I mean their construction, rather than results.

As bdavis notes above, the Glock trigger differs from many firearms, in that the trigger spring serves to pull the trigger, not return it. Recoil slide action serves to reset the trigger, and were there not something to prevent it traveling aft again, it's possible that it might fire under inertia. It's a low-mass trigger, however, and the trigger spring is relatively light.

The competition springs that lighten trigger pull are actually heavier springs; a heavier spring creating more rearward assist on the trigger bar assembly. By comparison, the P320 trigger spring pushes the trigger forward, and pressing the trigger opposes the spring. To create a lighter trigger on the P320, one can use a lighter trigger return spring, as the Grayguns competition trigger system does (in my pistols with the Grayguns trigger system, I use the stock factory spring, instead).

The action of the Glock trigger and the P320 trigger are quite different, so a comparison between the two for the sake of discussion of a trigger safety is more of an apples/oranges comparison.

The change with the "upgrade" wasn't so much the lighter trigger, but the internal addition to the FCU of the disconnector, a new, lightweight sear with a secondary notch to catch the striker if the striker is somehow released from the primary notch, a lightweight striker, and a machined disconnector notch in the slide, to work with the newly added disconnector.

With that change, Sig referred to the original, solid trigger as the "adverse trigger." Those who don't look beyond the exterior of the firearm might think that the "drop safety" changes with the "upgrade" were simply a lighter trigger, and thus think that a trigger safety might be in order. That thinking completely misses the point.

Sig's Phil Strader explains the changes and points them out individually in the following video:

https://youtu.be/u9vIY2EoJwE

The differences in the striker, trigger, and sear:

This message has been edited. Last edited by: sns3guppy,

On the subject, I remember years ago reading a study where they dropped the striker on Glocks at the normal compression point, and there was enough power to set off every round tested.

I have no idea where I read it, but it always stuck with me. That said, my Glock 19 is probably my most preferred pistol.