Welcome to part 2 of 3 of our Polymer 80 Ghost gun do-it-yourself project. Make sure you check out Part 1 for the down-low on 80% firearms, the kit I’m using, and what you’ll need to complete the build. These are not how-to on building these guns. Doing that in article form is difficult, and this is more of a commentary and review on the process. For how-tos I’d refer you to videos, they can show the steps in much greater detail.
Milling the PF940C frame involves cutting down four rail blocks. Once the Polymer 80 frame is snapped into the jig, it’s quite evident where and how much material you have to remove is. It’s everything not covered by the jig. I used a simple cutting bit to take off the blocks layer by layer. I ran the Dremel slowly to maintain reasonable control and chopped off the four blocks quite quickly.
This is the easiest part of the entire process. The plastic comes off easily, and then your goal is to ensure a smooth surface. A little polishing does the job, and on my previous build, I used a hand file to smooth things out.
After that, we need a drill and an endmill. If you look down the front of the Polymer 80 frame, you’ll see a large chunk of plastic where your barrel and recoil assembly will sit. This is the barrel block. This is a little trickier and requires some patience and a steady hand. I took it very slow and aligned the hand drill carefully with the barrel block. The portion you are milling is very evident and outlined in the polymer frame. Follow that cut out carefully, and don’t get too far ahead of yourself.
Once the majority of the barrel block is milled out, I used a Dremel to clean it up a bit and smooth things out. When it comes to aligning the slide onto the rear rails and making sure the ejector fits, you have had the make sure your barrel and recoil assembly are sitting right. If they are too high, they will force the rear of your slide to sit too high to go over the rails. Most of the fine-tuned work here will be near the bottom and should be done slowly.
Next, you have to drill six total holes. The first on the underside of the polymer 80 frame is quick and easy. The one that gives me trouble, me included, is the rear frame. There is a great video showing how to drill these holes. I messed mine up because even something idiot-proof doesn’t stand a chance against me.
I do feel better seeing this is a common problem. I drilled my holes and inserted the rear rails. Then, I tried to tap in the bolt and tapped a little overzealously. It bent the rail. This is my cautionary tale about this part. I sent an email to Polymer80 to see if I could buy a new rear rail. I described that I was dumb, and the Marine in me took over the hammer. Unfortunately, they don’t sell the rear rail as a stand-alone piece.
After several emails and me sending several pictures, I was offered to buy another frame for a discounted price. I was going to take this route, but luckily a rear rail popped up from a friend of a friend that had a kit he never built. We did some horse-trading a new rear rail was in my hands.
Polymer 80 Parts Installation
The rear and front rails are proprietary parts that are included with the kit. As I detailed above, I messed up on the rear rail. The front locking black rail system was easier to install. It slid right into the frame without issue. Give it a slight squeeze and maybe a soft tap, and it’s in.
From there, we install the magazine catch spring and magazine catch. This is fairly simple, but don’t lose the magazine catch spring. It’s small and easy to do on the black surface I was working on.
Next is the slide locking lever spring and stop. Again fairly simple and ingeniously designed.
The rear rail module is installed with the trigger. So you have the assemble the trigger kit, and then it slides in with the rear rail module. Because I messed up my kit a bit, I had to adjust my frame. I had to open up both holes on the frame because of my past mistakes. I opened them up and then installed the rear rail and added epoxy. This puts the holes back to normal size and holds the pin in fine.
Once the trigger is in, drop in the slide lock and follow it up with the trigger housing pin. Then push the pins for the lock block pin above the trigger pin. It all comes together so simply that the genius of the Glock design is present. It’s remarkably simple but has proven over time very effective.
Putting the Slide on Your Polymer 80 Frame
Slides can come complete or unassembled. Mine was unassembled, but again the design is so simple it’s hard to muck it up. Once your slide is together, you can slide it on to the frame. If it fits, be happy! If it’s very stiff, don’t worry, that’s somewhat normal. We’ll talk about how to fix that in the next article. Check it out at AmmoLand.
Want to build your own Ghost Gun? Here are links to more Polymer80 parts, 80% lower gun kits and tools.
- Polymer80 Manufacturing
- Polymer 80 Part at Brownells
- Polymer80 80% Lowers at Rainierarms
- Polymer 80 at Primary Arms