inconsistent resetting

[IDKsheet]

trouble shooting a great GST-9 lower with a non- OEM trigger kit. I love the grip geometry and the massive gas pedals.

I have 2 aftermarket slides with mixed results. both work fine (flawless resets) on a p940c frame and an OEM GLK lwr and TMH kit, but only 1 works on the GST-9 frame. I think it may have something to do with the thickness of the rear locking block rails. Conversely the milling of the slide rail cuts.

The GST-9 rear LBR are about 0.15-0.5mm (+/-) thinner than on the p80 hardware. the GST-9 rails are thinner and this translates to a slightly HIGHER rail surface for the slide to run on, thus giving the firing pin vertical catch just enough space to miss catching the cruciform.

The reset will happen when I release the slide and the trigger shoe is not depressed or if I push down on the slide as it moves fwd (with depressed shoe). I can see the vertical motion in the slide.

Question: what can I do to get the cruciform higher? or what mods to the cruciform can be done without undermining long term function, like bending the rear tab of cruciform up? will this just get pushed back down over time? adding material to the TMH surface which guides the cruciform up in height, doesn't seem doable as the cruciform guide slot would also need adjustment.
Perhaps trying a different TMH may be simpler, hoping that a slight realignment of the pin hole would raise the entire assembly?
Can 80 % ARMS offer thicker RLBR or can the GST frame accept a RLBR from p80 systems?

thanks

 

[GSW10]

GLOCK OEM TRIG W/TRIG BAR G19 PRE-EH

<p>Glock OEM Trigger with Trigger Bar, Fits G19, Pre-EH Serial Numbers, Marked '+' On Top of Cruciform, Black Finish SP01293</p>

www.glockmeister.com

This is your best option. The "Pre-EH" Trigger Bar raises the Cruciform for a more "Positive" Sear Engagement. Stamped with a "+".

The thin rails and questionable Sear engagement are the worst known-issue regarding the GST-9 on a technical level. Some of them, you get lucky and the engagement is fine. Some, you are not so lucky, and it is bad, like yours. Others, you get VERY unlucky, and the engagement SEEMS fine, and then it isn't (extremely in-depth testing procedures are called for on the GST-9). A LOT of it has to do with the specs on the particular slide you have too -yes they should all be the same, no they are not.

 

[IDKsheet]

@GSW10 thanks for that link and confirmation of their manufacturing specs issue. Seems thicker rails, even if only the top, horizontal flap that actually guides the slide, could be a simple re tool in production. The 2 piece RLBR design has other complications inherent to it, making the p80 version better in several ways.
The GST RLBR system uses a slot on one side and I imagine adjusting the thickness of the vertical portion of these rails would then compromise the specs of the entire rear RLBR/TMH cavity. Not sure I want to custom grind one to fit a p80 RLBR, but it could be a fun project.

BTW, what is "pre-EH" refer too?

 

[Mooner]

BTW, what is "pre-EH" refer too?

Helps with bad sear engagement, Pre-Eh triggers cruciform is bent up higher with stamped "+" More in-depth info in the following post.

Tip! - My goto trigger setup

Disclaimer: I am not an expert by any means. The market is flooded with aftermarket triggers, I only have experience with a few. This is MY setup, you have to figure out your preference. My Trigger Setup: Short version This is my goto setup for most of my builds now. I like this setup since...

www.patriotgunbuilders.com

Deep breath...."A Tale of Two Subcompacts" ….SOLVED!!

So good to be back here...missed y'all. So I took some courage and brought-out the two project pieces we discussed months ago, after hitting a brick wall with the squirt gun trigger phenomena in BOTH builds. Both had the identical parts procured from the same suppliers, and set-aside until I...

www.patriotgunbuilders.com

 

[GSW10]

@GSW10 thanks for that link and confirmation of their manufacturing specs issue. Seems thicker rails, even if only the top, horizontal flap that actually guides the slide, could be a simple re tool in production. The 2 piece RLBR design has other complications inherent to it, making the p80 version better in several ways.
The GST RLBR system uses a slot on one side and I imagine adjusting the thickness of the vertical portion of these rails would then compromise the specs of the entire rear RLBR/TMH cavity. Not sure I want to custom grind one to fit a p80 RLBR, but it could be a fun project.

BTW, what is "pre-EH" refer too?

"Pre-EH" refers to the Serial Number sequence of a batch of G19s Glock manufactured before the FGR models (what we now refer to as "Gen 2"). Prior to the "EH" series S/N, Glock had issues with poor Sear engagement, and manufactured a Trigger Bar with a taller Cruciform to correct it. I've been toying with the idea of machining some Rear Rails as well, but would be more interested in tackling the FRLB component, I would be interested in a custom variation using full-size (G17-type) spacing and 'bridge' specs in a Compact sized FRLB, to make top-end hybrids easier and more straight-forward to assemble. I have about a billion other projects to do first though...

Rook Tactical Rear Rails have been reported to be able to be modified to fit the GST-9, so that could be an option for you as well. Also check out Palmetto State's "Dagger" Rear Rails -they are cheap and readily available. Some work would certainly be required to make this fit the GST-9, but it at least offers a starting-point. https://palmettostatearmory.com/psa-dagger-rear-rail.html

 

[Racer7696]

Love to know id anyone here has custom fit the Rook ones in the gst

 

[IDKsheet]

Love to know id anyone here has custom fit the Rook ones in the gst

Love to know id anyone here has custom fit the Rook ones in the gst

I'm reluctant to go with ROOK, poor CS, no response regarding my question about the distance from the dowel pin to the bottom of the rail tab and not worth the gamble considering the cost. I think I will try PSA Dagger RLBR set first, a fraction of the cost. would have to cut the cross bar part and maybe reduce the thickness as GSTs (and p80) each have an engineered dimension to accommodate the TMH and frame. GST has those rail slot part of the frame too. 80% Arms did accept my suggestion to produce a refined rear rail option, I conveyed all this to them as well.
My measurement of 80% ARMs rear rail was 27.5mm (from the top of the dowel pin to the btm of the rail tab)
vs p80 was 27mm
This will control how much vertical slop the firing pin claw (based on rail cuts) can tolerate on the sear.
im not using OEM TMH or lwr kit, btw, its aftermarket from US Patriot Armory.
I did produce positive results with a modification of the TMH however!!
I slightly sanded the inside top part of the slot guide for the cruciform. This allows the cruciform/sear to travel higher towards the firing pin claw and produce a positive reset.

I received a couple of the "pre-eh" + trigger bars, but have reserved those for future work and to possibly increase the purchase contact on the sear. currently its only about .3-.5mm with the firing pin.
this the GST real rail

this is p80 RLBR

 

[GSW10]

I did produce positive results with a modification of the TMH however!!
I slightly sanded the inside top part of the slot guide for the cruciform. This allows the cruciform/sear to travel higher towards the firing pin claw and produce a positive reset.

I am very concerned about this statement. Basically, it sounds like you are allowing the Cruciform to rise higher in a modified Trigger Housing, relying on that to increase the Sear engagement to the minimum 2/3rds (or beyond, but why?)....

That isn't how it works. The top of the TH's Cruciform guide 'slot' may dictate the upper limit of the Cruciform's height, but the BOTTOM of that slot dictates the LOWER end of the Cruciform's position. THAT is the crucial position. Unless you are also shimming, raising, or otherwise modifying the lower edge of the TH's slot, then the Cruciform can still 'drop' to a lower level, meaning that you are falsely indicating a higher percentage of Sear engagement.

Don't believe it? Use an Armorer's back-plate, check your Sear engagement with your modified TH -looks good, right?, then use a small pick, punch or whatever you can reach in with, and push DOWN on the Cruciform... Now how does that Sear engagement look?? I know, you wouldn't normally stick something into that part of the firearm when it is loaded... But imagine a hard jarring impact on this weapon, and the weight of the Cruciform trying to push it downward with momentum carrying it away from the Striker lug. Now imagine this while the gun is in a holster with the nose pinched downward a little, and a full mag pushing upwards at the back of the slide as well...

I am glad you got the Pre-EH Trigger Bars, those are a great option for low Sear engagement issues. Bending the Cruciform is really a last resort, unless you have a LOT of practice and experience at it. It is a very fine line between bent enough to actually help, and bent too far and actually damaging or weakening the hardened Cruciform.

 

[One Ping Only]

Just saw this…had a few inconsistencies with reset on our first two GST9’s..I found online some advice as to the cause and to clean-up the area on the rear rail where this pic will show you….the vertical edge can be rough and cause just a bit of interference with the triggerbar/connector on that side. Just hit it with some fine sandpaper and follow up maybe with a buffing wheel. Worked for us…would likely clear up during break-in use as well, but ya gotta have reset!!

 

[One Ping Only]

If I may, I’d like to second what GSW10 about modifying your trigger housing as you describe. It’s very concerning, and I’d ditch that one and replace it with a new one. Truly.

 

[IDKsheet]

Just saw this…had a few inconsistencies with reset on our first two GST9’s..I found online some advice as to the cause and to clean-up the area on the rear rail where this pic will show you….the vertical edge can be rough and cause just a bit of interference with the triggerbar/connector on that side. Just hit it with some fine sandpaper and follow up maybe with a buffing wheel. Worked for us…would likely clear up during break-in use as well, but ya gotta have reset!!
View attachment 9404

the GST rear rails I received are 2 piece, that looks like a p80 which wont work in GSTs,

 

[One Ping Only]

the GST rear rails I received are 2 piece, that looks like a p80 which wont work in GSTs,

IDK- you have the MOD ONE version. Ours have the one piece, pre mod one rear rails. But the same thing applies. Make sure that vertical part of the right rail next to the connector & trigger bar are nice and smooth. Clean up any rough edges. Should help. I'm not saying this WILL cure your situation, but generally that's what causes a fail to reset in these as I understand it.

 

[IDKsheet]

I am very concerned about this statement. Basically, it sounds like you are allowing the Cruciform to rise higher in a modified Trigger Housing, relying on that to increase the Sear engagement to the minimum 2/3rds (or beyond, but why?)....

That isn't how it works. The top of the TH's Cruciform guide 'slot' may dictate the upper limit of the Cruciform's height, but the BOTTOM of that slot dictates the LOWER end of the Cruciform's position. THAT is the crucial position. Unless you are also shimming, raising, or otherwise modifying the lower edge of the TH's slot, then the Cruciform can still 'drop' to a lower level, meaning that you are falsely indicating a higher percentage of Sear engagement.

Don't believe it? Use an Armorer's back-plate, check your Sear engagement with your modified TH -looks good, right?, then use a small pick, punch or whatever you can reach in with, and push DOWN on the Cruciform... Now how does that Sear engagement look?? I know, you wouldn't normally stick something into that part of the firearm when it is loaded... But imagine a hard jarring impact on this weapon, and the weight of the Cruciform trying to push it downward with momentum carrying it away from the Striker lug. Now imagine this while the gun is in a holster with the nose pinched downward a little, and a full mag pushing upwards at the back of the slide as well...

I am glad you got the Pre-EH Trigger Bars, those are a great option for low Sear engagement issues. Bending the Cruciform is really a last resort, unless you have a LOT of practice and experience at it. It is a very fine line between bent enough to actually help, and bent too far and actually damaging or weakening the hardened Cruciform.

@GSW10 thanks for the insight, I will investigate for sure. The vertical stability of the engagement. For a little consolation, I dont EDC this weapon chambered, if that is the implication of hazard.
My fix offered a sear engagement delta from zero to only about 1/3, so not at the 2/3 min you refer to either. I was questioning what the standard tolerance for that is. TY!
You can see that the height is really applied most towards the rear of the TMH slot and tapers as it moves into fwd battery.

in the absence of better rail height indexing from the dowel pin a new TMH, (OEM likely) and pre-eh t.bar will be the best target solution.

Im not really interested in adding a shim or material to provide the bottom support you indicate should be there.

Here you can see the sear surface engagement percentage, with the sear surface Sharpied and then cleaned by the contact with firing pin. The highlighted photo shows it in fwd contact battery position.

 

[IDKsheet]

IDK- you have the MOD ONE version. Ours have the one piece, pre mod one rear rails. But the same thing applies. Make sure that vertical part of the right rail next to the connector & trigger bar are nice and smooth. Clean up any rough edges. Should help. I'm not saying this WILL cure your situation, but generally that's what causes a fail to reset in these as I understand it.

THe trigger bar in mine doesnt really contact that edge of the rail structure, i did do a little smoothing of the polymer corner in the same concern. IDK they had a MOD 2 version with different rail sets. can you offer a distance measurement, to of dowel pin to the bottom of the rail? TY.

 

[One Ping Only]

Sorry I'm not setup to give you those measurements you ask for, but it does appear by your highlight that the trigger bar is chafing/dragging on the polymer in your instance...you might also double check the rail area I pointed out to see if there are any rough spots...even on the inside surface that rubs the trigger bar. GSW10 also gave you some sterling advice. Though I've done 3 GST9's, I'm in no way an authority, and still a student. Just glad to be able to share what I've learned in hopes it will make another's project easier and more successful.

As I understand it, there is only the Original GST9V1 (as I have), and the MOD ONE. I haven't heard of a mod two yet, nor do they list one at their website as of today. Might also double check the fwd end of that trigger bar and watch for any possible frame interference.

 

[GSW10]

Okay, a few things...
-First, whether EDC or not, what I am seeing there is NOT safe. Should NOT be seeing live ammo yet -but you will get it there.
-Second, your Trigger Spring is in upside down -doesn't seem like it should make any difference, but it sometimes does.
-Third, use one of those Pre-EH Trigger Bars, and recheck your Sear Engagement -2/3rds (or 67%) is a MINIMUM. On a GST-9, I would suggest trying for a little more as a minimum, but since you have a MOD-1 that may not be relevant:
The original GST-9 used slightly thinner rear rails, relying on their superior length to keep the rear of the slide in place -this allowed the Rails to fit tighter slides without trouble, BUT it was discovered that on looser-tolerance slides, the GST-9 tended to have 'slide rattle' and excessive lift, essentially allowing the slide along with the Striker to literally lift away from the Cruciform and reduce the Sear Engagement to well below the minimum safe amount (a relatively small number of GST-9s actually experienced dangerous conditions due to this, but it did happen sometimes). I have not seen a MOD-1 in person, and have heard fewer and fewer issues regarding the Rear Rails, but additional testing is still advisable. Regardless, 2/3rds Sear Engagement is the absolute minimum permissible. Less than that, and it can go off if dropped, pinched tightly in a holster, knocked about heavily, or even just fail to catch the Striker lug, giving you a runaway pistol that will empty the mag on one trigger pull -yeah, the authorities don't like that very much, and it isn't safe at all.
-Fourth, given the amount of material removed from that TH, I agree with @One Ping Only that you should replace it -try an OEM Trigger Housing, I suspect that will help your Sear Engagement too. If you can get 100%, you are golden.
-Fifth, take some time and watch the Safety Video posted in the Resource Center here -very valuable info, presented better than I can do. Do NOT skip the drop-testing, make sure you try it empty and also with a mag full-o-dummy cartridges. ESSENTIAL testing! I HATE drop-testing, but it is essential to ensuring you have a safe and functional pistol. Remember, YOU are responsible not only for hitting your target, not only for NOT hitting anything EXCEPT your target, but also for making sure that firearm won't shoot something (including your leg) without you pulling the trigger. An 'accidental discharge' is 100% the same as a 'negligent discharge', especially when YOU are the Builder. Keep with it, you almost have that thing ready!

-Edit: Woops! And:
-Sixth, I guess this was Post #1,000...