Building a Glock Part 4: Finishing the Slide Parts Kit By: Jason Mosher


We installed the parts kit on a Glock 10 Gen 3 style frame in Parts 1 and 2. In Part 3 we started to install the parts kit to the slide. Today, we are finishing up our Building a Glock series with the slide parts kit installation and then we’ll head out to the range and take it for a spin.

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The parts kit on a slide is a little easier to install than it is on the lower frame. Neither one is hard, but I think the slide is easier. One reason is that you only need to remove the back plate to take everything off the slide. With the lower, you have to remove pins and take some parts off to get to others. But right now we have a slide to finish. Let’s jump in and finish up so we can see the final product.

Firing Pin Assembly

The firing pin assembly has a total of four parts. These are the hardest parts to assemble from the slide parts kit. But don’t worry, it’s not that bad.

To start off, place the firing pin sleeve over the firing pin. The firing pin will slide into the groove of the sleeve so that the part sticking up goes into the groove. Next, we need to install the spring and secure it with the cups. This is the part some people find tricky. To hold the firing pin up while putting on the spring, I used a 5/32 punch and an armorer’s block. If you do not have an armorer’s block, you can make one with a piece of 2×4 wood. Cut the 2×4 about 6 inches long and drill a few holes through it. Make the holes large enough for the back side of a punch to fit in the hole.

Glock slide and firing pin
The firing pin assembly includes (from left to right) the firing pin sleeve, firing pin, firing pin spring, and spring cups.

I placed the punch in the armorer’s block and placed the firing pin and sleeve over the punch. This helped me hold it up while installing the spring cups. The spring will need to be pushed down until a cup can fit over the small rounded portion of the firing pin. I find it easier to do one cup at a time. Once the first cup is on, push the spring down again far enough to place the second cup beside it. When both cups are on the firing pin, they will hold the firing pin in place (see photo below).

Firing pin assembly for Glock 19
I placed the firing pin and sleeve over the punch to help hold it up when connecting the spring cups.

Installing firing pin and plate cover

The slide cover will go on next. Use a small punch to push down on the firing pin so that it goes under the slide cover. Push the slide cover up just far enough to hold the firing pin down and then use the punch to push in on the ejector plunger. Once it is pushed in, the slide cover should push up the rest of the way. If installed correctly, the cover will go all the way to the top of the slide and you will hear a “click” as it falls in place.

Plate slide cover for Glock 19
The plate cover will slide on once the firing pin and ejector plunger have been pushed out of the way.

To remove the slide cover, turn the slide over so you can see the bottom of the slide. You will see the firing pin and spring through the open track. Use the punch to pull back on the firing pin (this takes pressure off the slide cover) and push the slide cover just enough to dislodge it. Once it has come loose, you can push it the rest of the way off. Be sure to keep your thumb over the back of the slide as you push it off so the firing pin and extractor plunger do not come out.

Installing Sights and Barrel

The last things to install on our slide are the front and back sights. The backsight is the hardest if you do not have a sight pusher tool. If you plan to replace or install sights on Glock pistols, I would recommend buying a sight pusher. I use the Real Avid Sight Pusher and it works great.

For this process, insert the slide into the sight tool and use the bottom handle to lock it in place. Then slowly turn the larger handle on the side of the tool so it can push the sight out of the slide. When installing a new sight, simply push the sight in the groove as far as you can by hand and then use the sight pusher to push it back into the center of the slide.

The front sight also takes a small wrench which comes with the Real Avid Sight Tool. They can also be purchased separately for just a few dollars. The screw for the front sight can be found on the bottom of the slide, near the front. If you are replacing it, just unscrew it and take the old one off. The new sight will sit in the hole from the top of the slide and the screw will secure it from underneath. The screw needs to be snug, but don’t over-tighten it.

Finishing Up

With the slide complete, we have now assembled a full Glock 19 pistol. When I started this project, I intended to build the lower and upper as a set. After finishing them, I decided I like the lower with the Bull Armory slide better than I do the slide that I built. This is one of the nice things about guns that are interchangeable. You can mix and match to your own liking.

I took both of these guns (one with the new frame and one with the new slide) to the range for a test. It’s always fun to shoot a gun for the first time if you built it yourself. Both of these guns fired without any issues just like you would expect from a Glock.

Glock build guns
The Glock lower in gray and the black slide with gold barrel turned out great.

The grey frame I selected goes nicely with the silver slide of my Bull Armory G19 and the Black slide with a golden barrel looks just as good with the Bull Armory frame. If you do have issues on the range, be patient and identify the problem. Take the gun apart and look for the part that’s causing the problem and correct it. The process is fun, even when you have to work out a few bugs. But when you’re done, you have a gun that you built and it looks exactly how you want.