Welcome to part one of a three-part series, a joint collaboration between The Truth About Guns, Ammoland, and USA Carry. We’ve started a new project that will include three articles going over the process of building your own Polymer80 GLOCK compatible 9mm pistol and getting it running.

The Polymer80 kit for this project was provided by 80-Lower.com. They sent me one of their complete GLOCK compatible pistol kits. This kit includes the Polymer80 80% frame as well as the lower parts kit, the slide and slide kit, and a small travel safe.

What is an 80% Frame?

If a gun’s frame or receiver is built, but remains unfinished, it’s not considered a gun…legally speaking. These unfinished frames and receivers are known as “80%” frames or lower receivers (in the case of an AR-15). The idea is that the buyer will do the last 20% of the finish work to make it operate, in effect building his own gun.

That’s something that’s been legal in the U.S. since forever, though now a few states prohibit home builds or require a home-built firearm to be registered and serialized. Be sure you know your state’s laws.

There’s a wide variety of 80% frame and receivers available today, including kits available for AR-15s, AKs, Ruger 10/22s, Sten guns, GLOCKs, and many, many more.

Again, since these are unfinished frames in the eyes of the ATF, the are not considered firearms. That means they can be shipped directly to your home. You don’t have to pay a transfer fee or fill out a 4473 background check form.

Federally it’s perfectly legal to build a gun for your own personal use. As mentioned above, however, that freedom varies among the states, with the demonization of home-builds as “ghost guns.”

A few states have regulated 80% builds, so be sure to check your state’s laws. The only other caveat is that our glorious Federal government says I can’t make these and sell them to anyone else. That requires a manufacturer’s license, but that’s another argument for another day.

The Polymer80 GLOCK frames are known by their official nomenclature as the PF940 series. They come in full-sized, compact, and subcompact models, as well as a G43 variant.

I went with the PF940C, the GLOCK 19/23-sized variant of these frames for this project. They also come in a rather wide variety of colors including black, FDE, OD Green, Cobalt, Titanium, and Gray.

Why Build Your Own?

Because to hell with gun control. Honestly, if you order a lower or a kit over the internet with a credit card, shipped to your home address, keeping it off the books isn’t guaranteed if someone starts looking hard enough. But building your own firearm this way makes it a bit more difficult to track you than a 4473 form would.

My reason for building one, though, is that I like guns, and I like having projects to work on. I’ve built one of these before and I find it to be fun and interesting. It gives you a very excellent view of how GLOCK pistols work and just how simple they are.

Best of all, at the end of the project, you have yourself a very good 9mm handgun.

The PF940 frames also feature better ergonomics than factory GLOCKs as far as I’m concerned. Especially the models prior to the Gen5 guns. They lack finger grooves, have a more 1911-ish grip angle, and feature a more aggressive undercut in the trigger guard.

There is also a more pronounced beavertail to the rear of the grip. I’ve a frequent victim of GLOCK slide bite, but not with this particular pistol.

The Polumer80 frams also feature a normal Picatinny accessory rail as opposed to GLOCK’s weird proprietary rail. The subcompact models have rails, including the G43 variant (GLOCK doesn’t offer that).

If you don’t go the kit route, there’s also the attraction of buying your parts one piece at a time and getting the exact components you want. I can certainly see why it’s easier to do get the parts you want up front and have it done rather than swapping out parts.

What You’ll Need to Finish the Kit

The Polymer80 kits come with a simple clamp-on jig, as well as the two bits and the endmill you’ll need to finish the pistol. In terms of tools, you can finish the frames a variety of ways.

A guy on Reddit did one with no power tools at all. I used a Dremel, a hand drill, a mallet, and a few punches, tools most people will have or can pick up very affordably. I also used a vise, but in my last build, I didn’t need one. A vise does make things much simpler, though, so if you have one, I recommend you use it.

The vise makes the process nearly idiot-proof, although, as we’ll see in this series, I’m a bit of an idiot. Once the jig is snapped over the frame, everything you need to do is aligned and ready to mill. There are no adjustments needed, and it’s all Dremel and drill work after that.

What’s in My Kit?

My complete pistol kit is pretty simple. I used a PF940C frame with a 9mm slide kit produced by 80-Lower. It’s a simple slide with forward and rear serrations and is all black.

I like that, for the most part, the kit is all GLOCK OEM parts. Nothing against the aftermarket, but the Polymer80 PF940C kit was built for GLOCK parts, so that’s the route I wanted to take. It may not be fancy or “custom,” but it will be reliable.

So that’s the lowdown on 80% frames, why you’d want one and what a kit gun like mine includes in the next sections, we’ll go through building the gun and then making it reliable.