Tag Archives: Glock

What To Do If Your Polymer80 or Glock Double Fires? It May Be Your Aftermarket Connector

A problem that can happen with a Glock-type of pistol is known as “doubling” wherein the pistol fires one round when the trigger is pulled and a second one when the trigger is released. For those of you all excited about learning how to build a binary trigger for a Polymer80 or Glock pistol, this is not the way to do it. The problem almost always happens when someone starts adding modified components vs. OEM Glock or goes polishing/sanding on parts.

Modifications to the fire control group can lead to unpredictable results because of stacked variation – this means that each little part can vary a little and when you add them all up, you can wind up with way more than the acceptable level at the end. With this in mind, you always want to test functionality before going to the range the first time and when you fire for the first time, load one round. The next time load two and remember to keep the pistol safely pointed downrange at all times.

I bet the pistol has been modified for this to happen

Okay, for a Glock design to double, somebody has altered the geometry of some of the parts through polishing or maybe they swapped parts, went to aftermarket parts, bent something, sanded on something, changed out springs that cause the firing pin lug to jump the sear — bottom line, something was changed. If you went with aftermarket parts, sanded or polished some of the fire control group and are now trying to figure out what happened, I’d recommend you replace whatever you touched with OEM Glock while you figure out next steps.

Today’s story focuses on the role of the connector

Well, Gaston Glock was a firearms genius and designed a unique fire control group (the trigger, firing pin, connector and what have you) that was unique at the time. One could argue a lot of companies have copied his design pretty closely.

Glock wanted both a reliable and safe pistol and the interesting thing was that he had no prior firearms design experience before the original Glock 17. Probably in part due to this, he came at the problem with an original point of view and created his “Safe Action System”.

What we want to focus on today is the connector. The connector is a metal stamping at the rear of the pistol connected to the trigger housing. When the trigger is squeezed, the connector forms a ramp that guides the trigger bar downwards thus releasing the firing pin. When the slide returns, the hook on the connector follows the track in the slide and the connector should move to the side allowing the trigger to reset . When the trigger is released it moves back into position for the next cycle. If the geometry is wrong for whatever reason, it will fail to block the firing pin from returning forward resulting in doubling.

The angled piece of sheet metal is the connector.
This gives you an approximate idea of where the trigger bar engages the ramp that the connector forms.

Let’s Watch A Video

To be honest, I feel like every time I watch a video or read something about the Glock design I learn more and sure don’t claim to be a Glock guru. I sure am a very interested user of the design though I prefer Polymer80 frames and their angle to an actual Glock brand pistol.

Watch this excellent animation on how a Glock works and pay attention to what the connector is supposed to do – this is what can go wrong with an aftermarket connector.

My Doubling Story

I took my brand new Polymer80 build G34 pistol to the range for testing and, hopefully some fun. A model 34 is basically a model 17 with a longer barrel and slide. My intent with it was to be a range gun so I tricked out just about everything. I literally think the magazine release spring, trigger block and extractor were the only OEM parts 🙂

When I took the pistol to the range and started test firing it was immediately apparent there was a problem because the pistol fired on the pull and release. It was inconsistent as well sometimes firing just one round and sometimes firing on the pull and the release. I was bumming because I meant to pack parts with me if I had a problem and forgot so it went back in the case while we tested other firearms.

So, what happened?

After I got home and started working on it, I realized I really hadn’t function tested it repeatedly enough. I definitely paid very close attention to what the pistol did when I released the trigger after racking the slide. I could replicate the doubling most of the time just like what happened at the range – it wasn’t doubling consistently during testing either, which is why I missed it.

Function testing going forward

Based on what I learned, here’s what I would recommend for function testing and do it 3-5 times before you go to the range:

  1. Absolutely make sure the pistol is clear / unloaded – both the chamber and the magazine.
  2. Squeeze the trigger just to make sure you are starting with an uncocked pistol.
  3. Rack the slide
  4. Pull the trigger – you should hear a click. DO NOT LET GO OF THE TRIGGER – Keep it pulled back.
  5. Rack the slide again with the trigger pulled
  6. Now listen carefully and watch the slide, when you get go of the trigger do you hear a click as the firing pin incorrectly goes forward? If so, you have a doubling problem.
  7. If you did not hear a click, go ahead and squeeze the trigger as you normally would and you should here the click of the firing pin.
  8. Now repeat steps 3-7 and pay attention when the slide cycles with the trigger being pulled. It should never fire upon release.

I had researched the springs and trigger carefully. What I questioned was the connector and it did turn out to be the Apex brand connector. To address the problem, I replaced it with a standard OEM Glock connector – problem solved. Note, this can happen with other aftermarket connectors as well such as Ghost so I am not singling out Apex. There’s no way a manufacturer can take all the possible combinations/variations into account so I don’t blame them at all – it simply happens and is something you should not be surprised about.

The top is the Apex connector and bottom is the OEM Glock connector that I installed. It’s interesting to see the slight shape differences in the angled surface that guides the trigger bar down.
There’s a trick you can sometimes do to swap connectors – not always but sometimes. This is the G34 that had the problem. First, press out the pin that holds the trigger block in place. By the way, ignore the Glost packaging to the left. I was looking at it and am too lazy to take another photo right now while I am writing this post 🙂
Sometimes you can gently lift the block out far enough to get a fingernail (or whatever) under the connector, lift it out of the block and then press the replacement in. That’s what I did here. I then reinstalled the block, its pin and function tested the pistol. It passed with flying colors after the swap.

A more thorough video on changing the connector from the folks at Brownells

In Conclusion

If I have time in the future, I may contact Apex and see what they recommend I do but for now, I’ll stick with the Glock connector. One of the key takeaways I want you to have is that it is important that you test your builds before you ever rely on them. If it fails, ask yourself – what did I just change and focus your efforts there.

Click here if you want to see other posts about Polymer80 pistols.

I hope this post helps you out.


Polymer80 and Glock Parts Vendors

When you want to customize your Polymer80 or Glock, or you need replacement parts, there are a number of solid vendors you can go to:

Those are all reputable vendors and aren’t going to sell you inferior counterfeit products.


If you find this post useful, please share the link on Facebook, with your friends, etc. Your support is much appreciated and if you have any feedback, please email me at info@roninsgrips.com.


Four Big Time Savers To Complete A Polymer80 Glock Frame

Polymer80 hit the ball out of the park with their 80% Glock compatible pistol frames. They provide frames that can enable a person to build a number of different models of Glock pistols that have some really nice enhancements including a 1911-grip angle and Picatinny rail in the front – the two features that matter most to me. At any rate, I have written a number of posts covering how to build and tune these pistols (click here if you want to open a new tab with them listed) and in this piece I want to focus on the four fastest methods I have found for completing the frame.

Read Now vs Tons of Troubleshooting Later

For a new builder, a Polymer80 is very do-able but don’t dive in without reading their instruction manual first, maybe read some of my past posts if you are building one of the models I have done or do some googling around for how-to guides/videos for what you are building. Any time you think you save on the front end will more than likely be blown on the back end trying to figure out why things don’t work right.

If this is your first build, please read the Polymer80 instructions for your model. You’ll save a ton of time and money if you can avoid a mistake in the first place. I can’t stress this enough.

So what are we talking about today?

There are four tips I want to share with you in this post:

1. Remove The Top Tabs Using Nippers/Nail Pullers

Folks, the fastest way to get rid of these tabs is to remove the jig and use nippers to snip off the tabs almost flush and then clean up with a file (if needed) and then sandpaper.

I took a pair of plain nippers and ground down the jaws to the are flush. Normally they are beveled on the top and the bottom for strength but you don’t need that if you’re just using them to cut plastic.

The small nippers on the left were ground down flat to cut the tabs as flush as possible. The unaltered nipper/nail puller on the right shows the typical beveled jaws that will leave more material behind for you to review. Note, even that is way faster than filing or milling off the tabs.

Cleaning up after the tabs are snipped off is up to you and what you prefer. I use a file to knock off any remnants and then lightly sand from 180, then 220 and finally 400 grit. My goal is to make it look good vs. a hack job.

If you don’t have a fair amount of experience filing and sanding then you might want to not use this approach. Speed is really for folks with experience using these types of tools

2. Drill The Pin Holes The Right Way The First Time

Drilling the pin holes is really straight forward and oddly enough, I am going to tell you not to do two things and add a third:

  1. Do not put the jig flat on a drill press. It was not designed for that. It was designed to be clamped at the bottom. Trying to drill it while it lays flat on a press will likely yield holes that are out of alignment.
  2. Drill the holes one side at a time. Do NOT try to drill straight through or little alignment errors become big alignment errors once you get to the other side of the jig.
  3. You need to be perpendicular to the jig when you drill – left-right and top-bottom. It’s easier to see left-right variation and fix that. It tends to be harder, at least for me, to see how my drill is up and down. My hand drills have levels built in and I use them to help. If you don’t have levels in your hand drill then either be very careful or use some type of straight edge that you can line up by.
My Ryobi 18 volt drill is ancient, beat half to death and has a small level up top that can really help. Note the bubble is to the front because the drill is just sitting on the bench.
The jig is designed to be clamped from the bottom!

3. Remove The Plastic In the Barrel Block Area

Now they give you a relatively giant end mill with the frame and it will shred stuff if you aren’t real, real careful. If you have a drill then take little cuts at a time with the frame clamped securely in the jig to something. In my case, I use a right angle jig.

Whatever you do, don’t treat the big end mill that comes with the frame like a drill bit because it isn’t. A drill bit is meant to bite in an penetrate. An end mill is going to go where the milling machine directs it and unless sufficient rigidity is there, the end mill will make a huge mess.

Also – obligatory safety notice – wear safety glasses. You only have one set of eyes and stuff does go wrong.
That is the barrel block and all material inside the “U” needs to be removed nice and flush with the sides. Failure to do so will result in your recoil rod hanging up on it and randomly locking the slide open.
Yes it looks like a drill bit but it is not!! That is the end mill that I am talking about and you also see my drill press that I use for grips and it has an X-Y table on it for fine adjustments. I really like it but to be very clear, it doesn’t turn your drill into a mill. A drill press is not designed for the side loads that a mill must deal with. For removing plastic, it works just fine for me. Trying to use it on metal will destroy the press. I have a milling machine for that type of work. I’m not using it because I am betting most of you have drill presses. If you don’t have a drill or a mill then use a hand drill to cut a series of small holes to the remove the tab and sand to clean it up.
When using an end mill, do a series of very small plunge cuts over and over. I had already done a couple of cuts before I took this photo. You’ll get a feel for how much you can mill off without the work piece rattling around too much. I remove a little and then move the table, remove a little and move the table over and over.

I use an old box to keep the sandpaper, dowels and popsicle sticks in. The large popsicle sticks are for me to wrap the sandpaper around to smooth the top of the frame where I removed the tabs. We have a new sanding kit that you can mount in your drill for clearing out the channel that can help speed things up dramatically.

4. Fitting The Slide To The Lower Receiver

I used to spend a ton of time polishing the parts by hand and a guy told me “Why are you doing that? Use lapping compound”. The funny thing was that I had two containers of Goodson Lapping compouned – 400 grit and 800 grit.

Don’t do this with the slide populated or trigger installed if you can avoid it. If you do, you’ll likely need to take it all apart to get rid of the grit anyways unless you are very careful. Yeah. I figured that out after I did it the first time and had grit everywhere.

Apply the 400 grit to the slide’s channels where the block tabs will engage. I typically use either a Q-tip or acid brush (I buy both in bulk) to apply the lapping compound and then work the slide over and over. It maybe a few times or a few hundred. On this CL, it was a few hundred. You then wrap up with 800 and it should slide very easily.

Remove the lapping compound when you are done. Use a polymer safe cleaner on the lower. Absolutely do not use brake cleaner, Acetone, or anything harsh like that.

I like Goodson brand lapping compound. You can get it off Amazon. I start with 400 grit and do the final polishing with 800 grit. They even offer a 1200 grit if you want it. I’ve found 800 is enough for me.

In Closing

I’ve only done a few builds but really enjoy making them and have learned a few tricks along the way. I hope this helps you out and click here if you’d like to see other Polymer80 posts.


Polymer80 and Glock Parts Vendors

When you want to customize your Polymer80 or Glock, or you need replacement parts, there are a number of solid vendors you can go to:

Those are all reputable vendors and aren’t going to sell you inferior counterfeit products.

How to Install Or Replace A Polymer80 or Glock’s Firing Pin Spring Assembly

Installing or replacing the firing pin spring in a Polymer80 or Glock pistol can seem daunting. It’s actually quite straight forward but you would never know it at first glance. I had to do some digging and want to share with you two videos that really helped me out.

Here are all the fun parts of both the firing pin and extractor plunger assemblies.
The top unit is the assembled firing pin group. The lower part is the Extractor Depressor Plunger assembly. I’m just showing the plunger because I had them together when I did the photo. You can leave the plunger alone.

Glock Striker Disassembly and Reassembly Video

Great Detailed Animation About The Firing Pin Assembly Specifically

Complete Glock Disassembly Video

In case you want to completely take your pistol apart, this is a very good video:

I hope this helps you out.


If you find this post useful, please share the link on Facebook, with your friends, etc. Your support is much appreciated and if you have any feedback, please email me at info@roninsgrips.com.