Finishing Your Polymer80 Frame: A Step-by-Step Guide

You’ve got a raw Polymer80 PF940 frame in your hands. The jig is tight, the rails are waiting, and those four tabs of polymer are blocking the trigger and rear rail modules. This is the critical first step, and doing it right sets the foundation for a reliable, precise build. Here’s exactly how to finish a Polymer80 frame, from drilling the pin holes to final assembly.

1. Tools and Workspace Setup

You don’t need a machine shop, but you do need the right tools. Start with a sturdy bench vise and the supplied Polymer80 jig. For drilling, a hand drill or drill press is mandatory; a Dremel rotary tool with cutting and sanding bits is highly recommended. You’ll need a set of drill bits: a 3mm bit for the locking block and rear rail pin holes, and a 4mm bit for the trigger and slide stop lever holes. Have a set of quality pin punches, a small hammer, a flat file, and 220-grit sandpaper ready. Good lighting is non-negotiable. Polymer80Gun offers complete jig-and-tool bundles that take the guesswork out of sourcing.

2. Drilling the Pin Holes with Precision

This is the most critical step for frame alignment. Secure the frame inside the jig with the provided screws, ensuring it’s seated completely. Using your 3mm bit, drill through the two marked holes on the front locking block rail first. Apply steady, moderate pressure. Next, flip the jig and drill the two marked rear rail module holes with the same 3mm bit. Finally, use the 4mm bit to drill the trigger housing pin hole and the slide stop lever pin hole. Always drill perpendicular to the jig surface. Do not force it; let the bit do the work. Clean the shavings from the holes after each step.

3. Removing the Polymer Tabs (The “Pocketing” Process)

The frame has three tabs in the trigger pocket and one in the rear rail cavity that must be removed. Using a Dremel with a cutting wheel or a sharp end mill bit, carefully cut away the bulk of the tab material, staying just inside the molded channel lines. The goal is to get close without touching the channel walls. Then, switch to a sanding drum or a hand file to slowly and evenly remove the remaining polymer until the pocket walls are smooth and the rail modules drop in flush. Test-fit the rear rail and locking block frequently. This process requires patience—you can always remove more material, but you can’t add it back.

4. Final Smoothing and Channel Lining

Once the rails seat properly, focus on the recoil spring channel. This area under the barrel must be perfectly smooth for the recoil spring to cycle without hanging up. Use your files and sandpaper to remove all molding lines and create a clean, U-shaped channel. Deburr all the pin holes with a round file or sandpaper. Finally, do a complete dry-fit of all parts: rails, pins, trigger mechanism. All pins should slide in with firm pressure from a punch, not fall in loose and not require a hammer to force. If a pin binds, carefully ream the hole with sandpaper wrapped around the drill bit.

5. Assembly and Function Check

With the frame finished, you can begin assembly. Install the rear rail module and locking block, securing them with their pins. Insert the trigger mechanism housing. Install the trigger assembly with its pin, followed by the slide stop lever. Before installing the slide, perform a full function check on the lower. Ensure the trigger resets, the slide stop lever moves freely, and the safety plunger (if your parts kit has one) works. Once satisfied, lubricate the rail channels and slide contact points. When you source your upper parts kit and slide from Polymer80Gun, you know you’re getting components designed to work with your finished frame.

How to finish a Polymer80 frame?

Finishing a Polymer80 frame involves drilling the four precise pin holes using the supplied jig and correct drill bits (3mm and 4mm), then carefully removing the polymer tabs in the trigger and rear rail pockets using a Dremel tool and files. The final steps are smoothing the recoil spring channel and deburring all holes before assembling the fire control parts.

How to complete Polymer80 frame?

Completing the frame is the machining process. To complete the build into a functional firearm, you must source a parts kit (LPK), a slide assembly (upper parts kit), and a magazine. After finishing the frame, you install all internal components, assemble the slide, and mate the two, followed by extensive function testing.

What is a Polymer80 frame?

A Polymer80 frame is an 80% firearm receiver, typically for Glock-pattern pistols, made from a proprietary polymer blend. It is not a firearm as sold and requires the user to complete the final machining (drilling holes and removing tabs) before it can accept fire control components. This allows for legal home building in most jurisdictions.

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Last updated: March 27, 2026