Building on the PF45: 10mm and .45 ACP notes for the large Polymer80 frame

The PF45 is the one Polymer80 pistol frame that is not a 9 mm or .40 build, and it has a few habits of its own.

Slides and barrels

Gen 3 G20 slides and barrels for 10 mm; Gen 3 G21 for .45 ACP. The slides are the same length and the frame does not care which you choose, but the barrel, recoil spring weight and magazines must match the caliber. Do not mix a G20 barrel with a G21 slide.

Grip

The PF45 grip is slimmer than a factory large frame, which is why people build it. It still takes standard 13-round G21 and 15-round G20 magazines.

Finishing

Same three cuts as the smaller frames; the tabs are larger and the barrel block wider, so budget more filing. The kit includes the jig, both rail modules, bits and end mill.

Recoil springs

Full-power 10 mm loads benefit from a heavier recoil spring than the stock G20 unit. A 20 to 22 lb spring on a steel guide rod is the usual choice; .45 ACP runs fine on stock weight.

Parts kit

A G21 lower parts kit fits both calibers; the trigger housing and ejector are the large-frame pattern.