PF940CL: Polymer80’s Compact Long Slide

If you thought Glock got it wrong when they released the Glock 19X to the civilian market, you’ll love what Polymer80 has in store for you. Intended as a military service weapon, the 19X has a 19-length slide and a 17-length grip. For the civilian market, with concealed carry as a primary use case, this is the opposite of what many might desire. The Glock 19 is already an immensely popular carry gun. And if you were to make a change to its overall packaging, you might rather eschew extending the grip — thus making it harder to conceal — and lengthen the slide instead. A shorter grip with longer slide is easier to conceal and provides a longer sight radius than the opposite configuration. And the Polymer 80 PF940CL is the perfect foundation to start from.

That’s exactly what Polymer80 did with its new PF940CL frame. It’s essentially a Glock 17-sized frame, accepting G17-compatible Gen 3 uppers and parts, with the grip chopped down to G19 length.

True to Polymer80’s roots, the PF940CL frame is first being offered as an 80-percent non-gun. In other words, the ATF doesn’t consider it to be a firearm — it’s simply a piece of polymer that needs additional machining before it becomes an actual gun. With Polymer80’s clever V2 frame design, all it takes is to drill six holes and cut away extraneous pieces of polymer. With the included plastic jig and tooling (two drill bits and an end mill), it’s a very straightforward process. Then, you simply install a front locking block that also incorporates front slide rails as well as rear slide rails that straddle the stock Glock trigger assembly. So, unlike Polymer80’s original V1 frame, all four slide rails are metal. Beyond that, it’s just like assembling a regular Glock. With the utter simplicity and low parts count of the underlying Glock architecture, the whole process is very straightforward.

And if you aren’t seeking the satisfaction of building your own gun or don’t care about a paper trail (subject to the laws in your jurisdiction), Polymer80 now also sells completed frames. In fact, because you won’t need the jig or tooling, a 100-percent frame is actually cheaper than an 80-percent frame — $135 versus $150 at MSRP for their current offerings. They’ve started offering their current frames as completed firearms, with the 100-percent, serialized PF940CL expected to be available later in 2018. We’re also seeing Polymer80 frames being used for semi-custom guns offered by other companies. For now, we got our hands on a preproduction 80-percent PF940CL frame, built it up, and wrung it out.

Making Freedom is Satisfying
Place the 80-percent frame in the jig and secure it in a bench vise. We added clamps to ensure it was properly aligned — but don’t crush it. With a hand drill and the M4 drill bit, drill the trigger pinhole. Drill the left and right side separately; don’t drill all the way through from one side. Then, with the smaller M3 drill bit, drill holes for the trigger housing pin and the locking block pin. Again, drill the left and right sides separately. Clean up the flashing that remains around the new holes. Polymer80 advises using a hand drill for this operation, not a drill press, in order to align properly with the guide holes in the jig.

Polymer80 offers a ReadyMod version of the frame with a completely blank grip that you can stipple or customize however you’d like.

While a mill would be a more appropriate choice, the next operations are often performed with a drill press by the typical garage tinkerer. There are four tabs that extend above the top of the PF940CL frame; they need to be removed to clear the slide. The requirement is basically to machine them off, keeping it level. Drill presses are technically only designed to take load in the Z-axis — i.e. drilling holes. But with the help of an X-Y table, you can secure the workpiece and use the table’s gearing to move it in the X and Y axes to machine away material. When working with softer material like polymer, this allows you to use your drill press like a mill. But you needn’t even use a drill press; we’ve seen folks use everything from Dremels to whittling knives.

In our case, we used a dirt-cheap $135 bench-top drill press from Harbor Freight along with their $75 cross slide vise. As it turns out, this bench-top drill press only has 10 inches of travel — in combination with the height of the vise, it was insufficient to accommodate the end mill and jig when placed on its end. Moreover, its table and base were small and only had two slots for attachments, lacking the typical X-shaped slots on larger machines that can secure items like a cross slide vise. It would have been easier to use a mill or a larger drill press, but we wanted to see how it could be done on a budget. So, in grand Wile E. Coyote school of gunsmithing fashion, we clamped the drill press and vise next to each other on a flat work surface, then rotated the drill press’ head away from its base to instead hover over the vise. This gave us enough clearance and travel to perform the remaining operations.

PF940CL compared to a stock Glock 19 from the early ’90s.

Drill presses such as the one we were using don’t have failsafe chucks. They’re simply pressed into place; they’re only intended to drill, not take loads laterally. So grab a mallet and beat the sh*t out of yours to secure it in place before inserting the end mill. And even then, keep an eye on it — more on this later.

Orient the jig horizontally with the tabs on the top and clamp it in the X-Y table. We again used additional clamps to keep all the corners secure, without overtightening. Set the appropriate depth for your end mill; we set it to bottom out when just kissing the jig. Familiarize yourself with how the gearing on the X-Y table moves the workpiece, so you know which direction to turn the cranks to make your cuts. Then machine off the tabs. Near the end of our last tab we noticed the drill press starting to complain. Just as we backed off, the chuck came loose. Fortunately, it didn’t make much mess of either polymer or flesh, but it stands as a clear warning to exercise caution, especially with these small, light-duty drill presses.

Differences from a stock Glock include the front locking block, additional locking block pin, rear slide rails, and a coiled slide lock spring.

The final step is to cut out a piece to clear the guide rod and barrel lug. Clamp the jig on its end and plunge the end mill into the dust cover of the frame to mill out a U-shaped opening, as indicated on the frame. Don’t cut beyond this point and be careful not to hit the jig with the chuck. It’s a little tricky to see what you’re doing, so we cut short of the relief edges and finished with a round file.

Remember that you can take additional passes to remove material, but you can’t add it back. So cut less rather than more — it’s easy to file away any excess. That’s exactly what we did, followed by a light sanding to smooth everything out.

Beyond this point, the only differences from assembling a regular Glock are the front locking block that doubles as front slide rails and rear slide rails that nest underneath the trigger assembly in the rear of the frame. Just insert them and secure with pins. We finished the build with a flat-faced curved trigger and PVD finished barrels and slides from Polymer80. We had two sets of the latter to try out. The match-grade barrels are available with and without fluting and made of 17-4 stainless steel. Barrels can be had in black DLC, titanium nitride, and stainless.

The Gen 3 slides are available in black, flat dark earth, and gray. Remaining parts were stock Glock, except for sights. On one slide, we installed Night Fision sights with tritium inserts — they were very bright; the company says they’re 30-percent brighter than other makes. The other slide was treated to Y-notch sights from Frank Proctor Shooting, with a fiber optic front and a rear notch cut in a Y shape to combine the precision of a narrow notch with the speed of a wider notch.

The end mill is used to remove tabs on the frame and cut a U-shaped area.

Bang Bang Bang

The completed gun felt great in the hand, though the slide was quite tight on the frame, in particular on the front locking block. Still, it passed our safety and functionality checks, so we loaded up mags and got to work.

Polymer80 recommends several hundred rounds to break in a new build. We brought out a mix of ammo with brass, aluminum, and steel cases. We experienced some failures to eject early on that went away, followed by periodic failure to feeds where the slide didn’t go completely into battery that persisted even as empty cases piled up, especially with steel cased Brown Bear ammo. The front locking block that came with our pre-production frame continued to bind on the slide and must have been out of spec. Fortunately, we had an extra locking block from an unfinished production Polymer80 PF940V2 standard frame. We disassembled the preproduction unit and compared the locking blocks. Our spare block slid easily and smoothly in the slide, while the original would bind. After swapping it into our build, the gun ran like a top with no further malfunctions. When you receive your kit, testfit the pieces; grab the loose locking block and your slide and make sure they slide smoothly.

The Polymer80 frame won’t fit in most Glock holsters, but a number of holster manufacturers make models specifically for it, including this one from Squared Away Customs.

Polymer80 incorporated great features on the frame, like those that custom builders toil for hours to add to stock Glock frames. The infamous Glock grip angle is mitigated by the flat backstrap, great for those who can’t get used to regular Glocks. However, if you like Glock grips, the difference is subtle enough that it shouldn’t be too hard to adjust. If you have large hands, the grip will feel almost as short as a G19 (helped by the undercut trigger guard), but you may appreciate the deletion of the finger grooves on the front strap. And if you have small hands, you’ll be able to get better purchase on the gun. The texturing is grippy without being too aggressive, though like with any grip texture an undershirt helps reduce discomfort on the ol’ beer belly. Contouring and undercuts on the trigger guard and the small beavertail allow you to get a comfortable, high grip on the gun. There’s also a small gas pedal cut on the frame in front of the slide lock for those who like to get some extra leverage on the gun with their support thumb; it’s also a nice spot to index your trigger finger. To make mag changes easier, the frame is scalloped out around the magazine release and the magwell is smoothly flared. All told, Polymer80 made excellent choices in their frame design that work together very well.

Trigger guard is contoured wonderfully, gas pedals are cut into the frame, and a standard Pic rail adorns the dust cover.

Most of the Glock holsters we had on hand wouldn’t accept our Polymer80 PF940CL. However, an ever-growing list of holster manufacturers offer compatible holsters. We got a Squared Away Customs P80 holster in sexy MultiCam; it’s stuffed down your pants, so no one will ever know, but like your favorite pair of underwear, it’ll put an extra spring in your step. Strapping on the gun helps you appreciate the original concept behind the gun —vertically, you don’t really notice the longer slide, and horizontally, the shorter grip doesn’t print as much.

As a carry-focused build, we kept the trigger mostly stock Glock, except for the P80 trigger shoe. It broke at 4.75 pounds with a hint of grittiness. The trigger shoe felt good, and we shot five-shot groups at 25 yards of just under 3 inches. In general, it shot like a customized Glock — and that’s a compliment.

Frank Proctor Shooting sights with a Y-notch on the left; NIght Fision sights with Accur8 single rear tritium dot setup on the right.

Even if you forgo the premium parts on this PF940CL for more economical selections, when you add it up, you may lament that it costs more than an actual Glock. If a Glock fits your needs, we encourage you to get one — all of us here at RECOIL have many of them. But if you appreciate the extra features on the Polymer80 frames, price out the cost of getting custom framework done on your Glock before you make your decision. You should check out Polymer80’s frames.

We really liked shooting and carrying the PF940CL; the anti-G19X format works well. If you want a Glock 17 with a 19-length grip — well, Glock doesn’t make one of those. And if you want to build your own gun, Glock can’t help you either. So, you know what you need to do. Build yourself some perfection.

Polymer80
PF940CL 80 Percent Pistol Frame Kit

Caliber: 9mm
Barrel Length: 4.5 inches
Overall Length: 7.6 inches
Weight Unloaded: 1.4 pounds
Magazine Capacity: 15
MSRP: $150 (frame kit only)
URL: polymer80.com

As featured:
> Polymer80 PF940CL 80-percent Pistol Frame Kit $150
> Polymer80 P80 G17 Gen 3 Standard Slide $325
> Polymer80 P80 G17 Barrel (Standard or Fluted) $165 or $175
> Polymer80 PF-Series Slide Parts Kit $100
> Glock Recoil Spring Assembly $5
> Glock Lower Parts Kit $50
> Polymer80 P80 Curved Trigger $100
> Sights (Frank Proctor Shooting Y Notch Sights or Night Fision Perfect Dot Accur8 Night Sights) $79 or $117
> Squared Away Customs P80 Holster (Multicam) $69
Total $1,043 – $1,091

The Polymer80 compact ran perfectly once we sorted out the front locking block. The frame’s features are well-thought-out and contribute to a secure, comfortable, and high grip.

[Editor's Note: This article originally appeared in CONCEALMENT ISSUE 11]

This article and more can be found in DIY Guns: RECOIL Magazine's Guide to Homebuilt Suppressors, 80% Lowers, and More.

More DIY Articles on RECOIL

• DIY Home Security Systems.
• DIY Double Barrel Slam Fire Shotgun.
• Solvent Traps and True DIY Suppressors.
• DIY High-Vis Targets.
• DIY 80 Percent Arms: The Condo Lower.
• DIY Trigger Job on a Springfield Hellcat.
• Walking through the ATF form 1 eFile process: Death and Taxes.
• True Gunsmithing: DIY Bolt Action Build.
• The 80 Percent Lower, the Ghost Gun, and the ATF.

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