A Build for Beginners – Polymer80 Step-By-Step

Some of you out there reading articles on building firearms are thinking “This is all well and good, but I don’t have a machine shop in my garage.” Or, you might have put together an AR and now you want to try something a little more challenging but still possible without a bunch of expensive equipment. Or maybe, you just decided you would like to build a sidearm to go with the rifle you build previously. If that’s the case, I had you in mind when I decided on this build.

I built this pistol using a minimum of equipment, with the equipment-challenged, a homebuilder in mind. There was a time when I fell into that category myself. Had things like the Polymer80 frame been around then, I would’ve gotten into homebuilding much sooner. Some tools are necessary, but I have opted to use tools that should be both small and inexpensive enough to be accessible to anyone, and a lot of folks will already have.

I’m going to show how to build one of the Polymer80 Glock style frames. Compared to rifles, there don’t seem to be as many options for 80% handgun builds. So I thought it would be something a little bit different to do. I have chosen their PF940Cv1, which is compatible with Glock 19 components. I chose this model because I did not yet possess a Glock 19. I went with a frame lacking any texturing on the grip portion of the frame; because that’s something I intend to add later once I get a feel for what I’d like on it. Polymer80 offers frames in a variety of models should you be after something else and I suspect they’ll all be put together about like this one.

Here are all of the parts as well as the frame, fixture, and tools supplied with the Polymer80 kit.

While I was in the process of obtaining parts for this build I was trying to keep the cost down. I went with pretty basic parts, and I looked for sales. Also, I intend to upgrade this pistol later after I shoot it some and decide what I want to improve. All in all, I didn’t do too badly, though you may do better. I bought the Polymer 80 frame from a local shop for $150, though you can find them for less. I’ve seen similar models on GunsAmerica for $120 or so. I bought the slide off of Gunbroker. It was listed as a blem, and it was $110. I bought the remainder of the parts from US Patriot Armory. These were the slide completion kit with barrel ($105), lower parts kit ($45), and sights ($10). That makes for a total of $420 without taxes or shipping.

As you can see, you can likely purchase a used Glock for less than it will cost you to put this build together. However, for me and I suspect a chunk of you reading this, that’s not the point. I enjoy taking a pile of parts and making them into a firearm. I enjoy figuring out how they work. Also given some recent political events, I think a lot of people can agree that there is some value in “un-papered” firearms.

Before beginning a project like this, make sure you understand all of the local, state, and federal laws that are applicable. It IS perfectly legal to build your own firearm in most places. However, in some localities, there are additional restrictions. I’m not a lawyer, and I live in a state that doesn’t restrict my right to build so long as I stay within the bounds of federal law. So I can’t say I’m familiar with the finer points of laws and regulations in those places where they do have restrictions on homebuilding firearms. Make sure you know what the laws and regulations are in your area before beginning!

The Polymer80 frame has a metal plate molded into it for a place to put a serial number. You can purchase serial numbered frames, or have your 80% frame engraved prior to starting work on it, should local laws require or you desire to have it marked. You can also mark it yourself, but I would not recommend using metal stamps for this task.

I believe in some places it is required to have even 80% receivers serialized. Fortunately, Polymer 80 offers serialized frames and there are some other places that will engrave your frame with a serial number. Beyond the legal obligations of some locales, some kind of serial number is advisable. In the event that your homebuilt firearm is stolen, it will give it a way to be identified and hopefully returned. Several years ago I had a few homebuilds stolen along with a bunch of other firearms. While I had marked them, I used some pretty generic serial numbers. To date, none of those builds have been recovered. I have often wondered if I might have gotten them back had they been marked with a more distinctive serial number. Now on all my builds, I do just that, because you just never know. Now that all of that is out of the way, on to building!

The frame and fixture are set up in the vise. These are made of polymer, and it will flex. Make sure you do not overtighten the vise. This will cause your pinhole locations to be off due to the fixture flexing.

The Polymer 80 Frame came with a fixture, as well as the drill bits needed to complete it. A lot of people building firearms are using drill presses or milling machines to “machine” these. After doing some looking I came to the conclusion that it was not really necessary to have that kind of equipment for this project. I used a hand drill, a Dremel tool, a couple of files, a vise, and some abrasive cloth (sandpaper would work). You could even leave out the Dremel tool and just use the files. An Exacto knife is pretty handy to have as well, particularly for deburring. You’ll also need a small hammer and some punches for installing the components on the frame.

The frame kit comes with the 2 drill bits needed to drill the holes in the frame. They are fairly close in size (3 and 4 mm) so make sure that you use the correct bit in the holes that are marked for it.
Drilling the pinholes in the frame. Drill one side, and then the other. Do not try to drill all the way through both sides.

The first task to be completed is to drill the pinholes in the frame. Polymer80 recommends this be done with a hand drill, using the drill bits supplied with the frame. This kind of surprised me when I first read it. But that’s what they recommend, and it fits pretty well with my theme here anyway. Pay close attention, because there are two different sized drill bits, and they’re not that much different in size. Make sure you use the right drill bit for the right hole. The holes on the fixture are marked with what size they should be drilled, so this isn’t too hard to get right if you’re paying attention. Do not try to drill all the way through the frame from one side. Drill one side, and then turn the fixture around and drill the other side.

The pinholes in the frame after drilling.
A Dremel is being used to remove the majority of the rail block material. I chose to use a steel cutter bit in the Dremel for this task, as it didn’t seem to plug up. The Dremel tool will want to “dig into” the material, so be careful and leave some material. This will prevent cutting into the frame with the Dremel.

The rail blocks on the tabs are molded on top of the frame to ensure that a slide won’t fit. Obviously, these need to be removed. I used a Dremel tool to remove most of the material. It is REALLY easy to cut too deep with the Dremel. The instructions from Polymer80 say Dremel tools can do WLDQ (a Whole Lot of Damage Quick), and this is definitely the case. So, I left some material as a “buffer area” and I removed this material with a file. An Exacto knife comes in handy for removing the burr that’s created from the Dremel tool, so that you can see what you’re doing a little better. The directions from Polymer80 said to remove material until the frame is even with the fixture. This is a pretty good indicator, but you can pretty well see when you’ve gone far enough if you’re paying attention. Then use the abrasive cloth (or sandpaper) to smooth things out for aesthetic’s sake.

I left some material to be filed off after using the Dremel. The purpose of this was to ensure that I didn’t go too deep with the Dremel tool.
I used a file to remove the last of the material on the rail blocks. Your file will clog with polymer as you’re doing this task. Clean it often. Avoid the temptation to use a coarse wood file or rasp to get around this problem. It will leave gouges in the soft polymer that you will not be able to remove.

Removing the barrel block is the next step. It’s a little bit trickier to get this done than the rail blocks because you don’t have a lot of room around it to work. Just like the rail blocks, I used the Dremel to “rough” out the area and finished it up with a round file. This area is a bit more critical because parts have to pass through the opening, and the remaining shelf is also necessary. Don’t get in a hurry. Go slow and remove a little bit of material at a time until you are finished.

This is the barrel block. You can pretty clearly see the material in the center that needs to be removed. Don’t cut into the rest of it, as that flange is a necessary feature on the frame.
I removed most of the material from the barrel block with a Dremel tool. I left a bit more for filing this time because it’s harder to see your progress on this part. Take your time when working on this feature and check your progress often.

The slide I purchased lacked any kind of metal finish, which you may have noticed in the earlier picture. I had some Brownells Aluma Hyde II in FDE leftover from a previous project, so that’s what I used on the slide. I’m not going to go into the finer points of that here, as almost all of the slides you can purchase already have some kind of finish on them.

I’m using a round file to remove the remaining material from the barrel block. It’s kind of tricky because you don’t have a lot of room to work. Just like the rail blocks, your file will clog up with polymer rather quickly. Stop and clean it when it does.
The Barrel Block has been filled out. You can use some abrasive cloth or sandpaper to smooth it out after filing.

Once the frame has been completed it’s time to assemble the components. Assembly of Glock pistols has been covered many times before and the information is readily available so I’m not going into detail here about that. You can buy preassembled slides if you so desire. Not that it’s that difficult to assemble a Glock slide. I will say that it would be advisable to put the pins in the frame before you install the other parts to make sure they go in place properly. You definitely want to make sure that you remove any remaining burrs left from drilling the pinholes before you proceed. It’s also definitely worth a look in the instructions at the various “tight-fitting suggestions” they have before you start putting parts in the frame.

The frame is ready for assembly.
The little burrs from drilling the pinholes will make assembly much more difficult. Make sure to remove them before assembling your frame.

Once everything is put together, it’s time to do some functional testing. We need to make sure that our trigger mechanism and other parts are working properly before we attempt to test fire it. First, I function test “dry”, or without dummy rounds. You definitely don’t want to perform any function testing with live rounds for safety reasons. At any rate, after ensuring that the pistol contains no ammunition, pull the trigger. While holding the trigger back, pull the slide all the way to the rear and release it. Then slowly release the trigger, while listening for the “click” of the trigger resetting. Then pull the trigger again. If the pistol fails to do any of these things, there’s something wrong in your trigger group. STOP AND CORRECT THE PROBLEM BEFORE PROCEEDING. After I’ve done the initial function testing, then I cycle the pistol with some dummy rounds. I do the procedure above, with the addition of ensuring that the dummy rounds feed, chamber, extract and eject properly. You also want to ensure that the slide lock holds the slide open after the last round ejects.

The assembled frame.

 When it came time to cycle the dummy rounds and test fire, I ran into a little snag when I realized that I didn’t have any Glock 19 magazines. The other Glock pistols I have owned have been full-sized models. Fortunately, magazines for the full-sized pistols work in the compact models of the same caliber-though they stick out a bit. So, I test-fired this build with a Glock 17 magazine.

The completed pistol.

As you can see, it is quite possible to build a firearm without needing a bunch of expensive equipment. It’s very possible that you already have the tools I used to complete this build. The Polymer80 frames really make it possible for almost anyone with a little bit of mechanical aptitude to build a nice pistol. Hopefully, this article has inspired some of you would be homebuilders to give it a shot!

For more information visit Polymer80 website.

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About the author: Christopher Mace Christopher Mace enlisted in the US Army as an Infantryman in 2001. He served in the 82nd & 101st Airborne Divisions, with four deployments to Afghanistan & Iraq. Chris started hobby gunsmithing in 2005. After completing his service in 2010, he earned AAS degrees in Machining as well as Welding & Fabrication. Chris has taken several armorers courses on different firearms, and has built several different types of firearms. He has been collecting & shooting military firearms, old and new since he was 18. He is currently pursuing a Gunsmithing Technician Certificate from Trinidad State Junior College. Chris enjoys repairing, customizing, building & assembling firearms, as well as different disciplines of competition shooting.

{ 4 comments… add one }
  • Chezwatts April 28, 2020, 10:11 am

    Good write up. I tried to use a drill press and lathe bits first time I did one (P80 says don’t use drill press), and the lathe bits dug into the material and frame. Like your approach, Slow and steady is the word.

    As an alternative to dremel, on my most recent build I used Stanley 1/2 inch end cutting pliers ($20 on Amazon) to snip off the tabs, that was a much cleaner and easier operation. Give that a try.

  • Christopher Mace April 27, 2020, 12:41 pm

    I don’t think there is a way to completely avoid having to clean up the pinhole burrs. Any time you drill a hole, you’re going to end up with something, though it might be small enough that you don’t notice unless you really look.

  • Steve Houts April 27, 2020, 12:19 pm

    I’ve done of these builds and the author is correct! Very simple and very easy with no specialty tools required! I’m very pleased with it and shoots great!

  • MagnumOpUS April 27, 2020, 11:17 am

    Good write up, Chris. You’ve removed much of the element of the unknown about tackling this kind of project. Looks like for someone who’s assembled ARs that this would be a lateral move.

    The pic of the drill hole burrs makes me wonder if buying a high quality drill bit, i.e. sharper, or even using a different type of bit would produce no to little burring?

    I am certainly more interested in doing one now.

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