Gen 3, Gen 4 and Gen 5: which Glock parts work on a Polymer80 frame

Polymer80 pistol frames are cut to the Gen 3 pattern. That one sentence answers most compatibility questions, but the detail matters when you are looking at a parts bin.

Slides

Gen 3 slides fit. Slides sold as Gen 3 and 4 compatible fit, because that phrase describes the slide rails, which are common. Gen 4 slides paired with their dual recoil spring assembly will run on a Gen 3 frame only with a Gen 3 recoil assembly and barrel. Gen 5 slides have a different front profile and locking block relationship and do not fit.

Barrels

Follow the slide, not the frame. A Gen 3 barrel for the model your slide copies is the safe answer. Threaded barrels change nothing about fit.

Triggers and fire control

Gen 3 and Gen 4 trigger bars are interchangeable in practice. Gen 5 trigger bars are not, because the ejector moved into the trigger housing and the geometry changed.

Locking blocks

Gen 3 frames use the three-pin or two-pin locking block depending on the model generation being copied. The Polymer80 frame kit is built around the Gen 3 block that comes in a Gen 3 parts kit; do not substitute a Gen 4 block.

Magazines

Generation-agnostic. A Gen 5 G19 magazine works in a finished PF940C.

Sights, guide rods, small parts

Sights follow the slide. Guide rods follow the slide generation. Slide stop levers, magazine catches and springs follow the frame, so buy Gen 3.

The short version

Buy Gen 3 for anything that touches the frame, and match the slide for anything that rides in it.

This is general information, not legal advice. Laws on unfinished frames and receivers vary by state and city and change often. Check the current law where you live before ordering.