Description

Polymer80 PF45 80% Large Frame Kit — The Foundation for Your .45 ACP or 10mm Build

Among all the 80% pistol frame platforms available, the Polymer80 PF45 occupies a unique position: it’s the only large-frame Polymer80 option, engineered specifically for Glock 20 (10mm Auto) and Glock 21 (.45 ACP) Gen 3 compatible components. If you’re building for stopping power, the PF45 is where you start.

California Gun Shop maintains a comprehensive inventory of 80% lower receivers and frame kits. Browse our complete 80% Frames category to see all available options, or compare the PF45 against our PF940v2 full-size 9mm frame and PF940SC subcompact kit. For those who want the compact long-slide format, we also carry the Polymer80 PF940CL.

What Makes the PF45 Different

Every other Polymer80 frame is designed around 9mm and .40 S&W — calibers where slide mass and frame strength are relatively moderate. The PF45 is built to a different specification entirely. Its wider magazine well, reinforced locking block pocket, and thicker dust cover are all engineered for the dimensional requirements and operating pressures of 10mm Auto and .45 ACP.

This isn’t just a scaled-up 9mm frame. The polymer composite formulation, wall thicknesses, and internal geometry have all been optimized for large-frame operation. The result is a frame blank that doesn’t flex under sustained large-caliber firing — and won’t show the cracking around the locking block area that improperly reinforced polymer frames sometimes exhibit after hard use with 10mm loads.

Kit Contents

• One PF45 80% large frame blank — Black, FDE, OD Green, or Gray
• Billet aluminum top and bottom jig plates
• Drill bit set for trigger cavity operations
• End mill bit for rail section machining
• Complete hardware and fastener package
• Illustrated step-by-step instruction guide

Full Specifications

Feature	Specification
Manufacturer	Polymer80
Model	PF45
Completion	80% — machining required
Glock Compatibility	G20 (10mm), G21 (.45 ACP), Gen 3
Calibers	.45 ACP, 10mm Auto, .40 Super
Frame Format	Full Size / Large Frame
Slide Compatibility	4.61″ G20/G21 format
Magazine Well	Wide body — G20/G21 double stack
Frame Polymer	Reinforced composite — fiberglass-filled
Grip Angle	Ergonomic 17-degree Polymer80 angle
Trigger Guard	Undercut for high-grip purchase
Picatinny Rail	Yes — integrated front accessory rail
Jig Material	Billet 6061-T6 aluminum
Origin	Made in USA

Required Parts to Complete the Build

• Glock 20 or G21 compatible slide and barrel assembly
• 4.61″ barrel in 10mm Auto or .45 ACP
• Glock Gen 3 large frame lower parts kit
• PF45-specific Rear Rail Module (RRM) — different from PF940 RRM
• Large frame Gen 3 locking block
• G20 or G21 compatible double-stack magazines
• Front and rear sights for the slide

Our accessories inventory includes compatible components. See our ROOK Tactical Rear Rail System for PF45 for a reinforced stainless steel RRM upgrade. We also carry the ROOK Tactical Front Locking Block Upgrade for PF45 and the Polymer80 PF45 Dimpled Pin Kit for a complete hardware upgrade.

The Case for 10mm in 2025

Ten-millimeter Auto has staged a remarkable comeback. Once considered a niche caliber, 10mm now sits at mainstream availability with factory ammunition options from Federal, Hornady, Underwood, DoubleTap, and others offering everything from downloaded practice loads to full-power hunting rounds exceeding 700 ft-lbs of muzzle energy.

The PF45 platform in 10mm offers something no factory pistol can match: a custom-built 10mm with exactly the slide serrations, barrel quality, trigger pull weight, and sight system you choose. Competition shooters, hunters, and outdoorsmen all have different requirements — the PF45 lets you optimize for yours.

Pros and Cons

Pros:

• Only Polymer80 frame for .45 ACP and 10mm — unique large-frame platform
• Fiberglass-reinforced composite rated for sustained 10mm Auto use
• Ergonomic Polymer80 grip improvements over factory Glock large frame
• Full jig kit included with all required bits and hardware
• Wide G20/G21 aftermarket ecosystem
• American manufactured

Cons:

• 80% — requires machining before assembly
• Large frame format — not suitable for concealed carry in most configurations
• PF45-specific RRM is a separate purchase
• California legal restrictions apply (see notice below)

⚠️ California Legal Notice — 80% Frames

California law (Penal Code 29180–29184, as amended by AB 1621 and Senate Bill 1) imposes strict requirements on the manufacture of unserialized firearms in California. Before machining or completing any 80% frame, California residents must:

1. Apply to the California Department of Justice (DOJ) for a unique serial number through the official DOJ Firearms Application Reporting System (CFARS)
2. Engrave or permanently affix that serial number to the frame prior to beginning assembly
3. Comply with all applicable handgun roster and feature requirements for the completed firearm

The purchase of an unfinished 80% frame blank may be permissible under California law in certain circumstances, but completing it without the required DOJ serial number is a criminal violation. California Gun Shop provides this information for educational purposes only. We strongly urge all California residents to consult a California-licensed firearms attorney before purchasing or completing any 80% frame.

Frequently Asked Questions

Q: Is the PF45 compatible with full-power 10mm loads?

A: Yes. Polymer80’s reinforced polymer composite formulation and the PF45’s structural geometry are specifically designed for 10mm Auto operating pressures (SAAMI max 37,500 psi). Many PF45 owners run thousands of rounds of full-power 10mm loads without frame issues. For extended high-volume use, aftermarket stainless steel locking blocks (such as those from ROOK Tactical) provide additional durability margin.

Q: Will .40 Super work in a PF45 build?

A: Yes, .40 Super uses the same G20 frame and barrel footprint as 10mm Auto. The barrel is the key component — you need a .40 Super-specific barrel to shoot .40 Super. The frame itself is caliber-neutral; it’s designed around G20/G21 physical dimensions, not the specific pressure levels of a single cartridge. .40 Super operates at higher pressures than 10mm, so use quality components throughout the build.

Q: Can I mix a G21 (.45 ACP) slide on a PF45 frame loaded for 10mm?

A: No. The barrel, chamber, and breech face geometry differ between .45 ACP and 10mm. You must match slide, barrel, and magazine to your chosen caliber. The frame is compatible with either caliber by design, but individual build components must be matched. A 10mm build uses G20 slides and 10mm magazines. A .45 ACP build uses G21 slides and .45 ACP magazines.

Q: How long does completion take?

A: Most builders complete the PF45 machining in two to four hours. The billet aluminum jig provides all the drill and mill guide surfaces needed. A drill press is strongly recommended for perpendicular, consistent hole placement. The instruction guide breaks the process into clear numbered steps. First-time builders may take longer — take your time for best results.

Q: What should I do with the completed frame regarding California serial requirements?

A: California residents who choose to complete an 80% frame must obtain a DOJ serial number through CFARS (the California Firearms Application Reporting System) before beginning any machining. The process involves submitting an application online and receiving a unique serial number that must be engraved on the frame. Do not proceed with completion before obtaining this number. Consult a California firearms attorney for specifics on your situation.