How To Finish a Polymer 80 Glock Frame Kit – Full Review

Several weeks ago I was walking around my favorite gun store, BMC Tactical in Albuquerque, New Mexico, when I saw a fancy looking Glock lower frame sitting in a plastic jig.

“What is that?” I inquired.

The clerk working the gun counter pulled the assembly out of the case and explained that it was Polymer 80’s PF940C Compact frame for a compact-sized Glock pistol.

“Sold. Do you have a lower parts kit?” I asked.

Beginning the Build

I walked out of BMC Tactical, drove home, and went straight to my armorer bench. Placing the Polymer 80 frame in the plastic jig, I squeezed the jig assembly in a typical work vise under my vertical drill press.

After attaching the supplied end mill in my drill press chuck, I turned the drill press on and started to remove polymer. The end mill sliced through the polymer like butter. After slowly and methodically removing all necessary polymer along the top of the frame, an act which took a whopping 10 minutes, I cut the slot in the frame that interfaces with the guide rod. After milling off as much plastic as possible with the end mill, I used a standard hand drill to bore holes for the pins that hold the internal parts. Polymer 80 provides two small drill bits for these holes. Note that the manufacturer does not recommend the use of a drill press for this step.

Assembling the Lower Parts Kit

After drilling out the holes, I used a set of Ramrodz Diamond Tipped Tweezers to smooth out the edges of the milled plastic. I assembled the lower frame kit and attached the slide assembly.

Initially, cycling the slide felt gritty. I disassembled the slide from the frame, lubed the pistol, re-assembled, and cycled it 100 times. After 100 cycles, I cleaned the pistol, relubricated it, and cycled 100 more times. I repeated this process until I had cycled the pistol a total of 500 times. After 500 cycles, the pistol felt smoother but was still difficult to rack. The slide was particularly tight when I held the trigger to the rear. I did an armorer level inspection, determined that the Glock Safe Action system would work properly, and drove out to my local range to test the pistol.




Since it was dark, I attached a Streamlight TLR-1 pistol light and hung an Action Target gong at 15 yards. I fired off 100 rounds of Remington 115-grain 9mm ammunition. The pistol required an aggressive grip to function and would fail to eject if my grip was loose. Time to hand fit.

Hand Fitting a Glock Pistol

When I held the trigger to the rear, the slide was damn near impossible to rack. This problem was the first I wanted to address through hand fitting. When a Glock trigger is in the rear position, the part of the trigger bar that interfaces with the firing pin safety is at its highest point. This position means that it makes contact with the bottom of the slide. Interestingly, the first time I attached the slide to the lower frame, the slide got stuck. The trigger bar got stuck distal to the firing pin safety. Removing the spacer sleeve and firing pin assembly allowed me to separate the slide from the lower frame. With a diamond file, I removed metal from the trigger bar until the bar and firing pin safety could interface correctly. This area was then sanded with 2000 grit sandpaper and Brasso.

From this picture, you can see where the trigger bar was getting hung up and grinding near the firing pin safety. I had to file and polish the trigger bar.

Rear Rail Module

Another area that I wanted to improve during the hand fitting process was the Rear Rail Module, proprietary to the Polymer 80 frame. On a factory Glock pistol, this part is molded into the plastic. On a Polymer 80, it is a stand-alone piece that houses the Trigger Mechanism and is pinned in place along with the Trigger Mechanism. The rails were sharp and rough. After going over them several times with a diamond file, I sanded them with 2000 grit sandpaper, then polished them with Brasso. I also polished the Trigger bar and Connector.

The two areas that I had to file and polish were the rear slide rails and the trigger bar.

Removing a little bit of metal off the trigger bar and polishing the rails on the Rear Rail Module worked wonders! After reassembling the slide and lower frame, I cycled the pistol, and it felt like a factory Glock. I cleaned and lubricated the pistol then conducted a pencil test. I cycled the pistol, then dropped a pencil down the barrel. Pointing the gun in the air, I squeezed the trigger. I was pleased to see the pencil jump several inches. This test checks to make sure that the Glock Safe Action System is working and that the pistol will fire.

More Range time

Heading back out to the range, I fired 100 rounds of PMC Bronze, Remington UMC, and Tula. The pistol performed flawlessly.

I personally did a little bit of stippling under the trigger guard and on the frame next to the Locking Block. The ergonomics on this pistol are fantastic.

The final round of testing took place during a pistol course taught by QPro Defense. Former Recon Marine Oscar Sanchez led the course, which was excellent: the instruction was top notch, the drills were relevant, and the coursework was current. I ran the Polymer 80 pistol for about half the course, and it performed 100%.

Final thoughts

So why did my Polymer 80 need the fine-tuning? My best guess is that my Rear Rail Module sat a little bit higher than average. This difference caused my trigger bar to put extra tension on the bottom of the slide. I have conferred with others who have also completed the kit, none of whom experienced the problems I discussed here.
All in all, finishing the Polymer 80 Compact lower frame kit was a lot of fun, and took surprisingly little time. The Frame itself has some nice additions, such as an enlarged back strap to mitigate slide bite, and comes with beautiful stippling. The ergonomics on the frame are superb, and this pistol is a joy to shoot.

Build one! The Polymer 80 Compact kit sells for around $150. If you have questions, feel free to comment below.

#60020 Diamond-Grip Pivoting Pinch Files

For more information about BMC Tactical, click here.

To purchase a Glock pistol on GunsAmerica, click here.

For more detail about the Polymer 80 Frame, click here.


{ 26 comments… add one }
  • Moldyolddude March 5, 2018, 2:28 pm

    I see there is a metal piece where the serial number is usually placed under the frame. Is that on all the LWD 19 frames ? If so where and how would you get a number to put in it if in the future all “Ghost” guns are made illegal ?

  • ejharb February 12, 2018, 9:17 am

    I kinda want to do a couple of these.
    9mm and 45.probably need to do it soon.if we lose our fantastic president or we get complacent and the demoncraps get back in power and evict him ghost guns are near the top of their list.I give it under 2 years before a mass shooting is done by one as a false flag to ban them.

  • Mike Leonetti January 29, 2018, 4:11 pm

    I have been looking at these for a while, but when searching for the other parts, it seems that the cost would be more than buying a brand new Glock. I would love to make one, but it doesn’t make a lot of sense to me.

    • ChAsM80 January 29, 2018, 5:36 pm

      If you shop carefully you can get the price down to about the same as a new Glock, and have some good parts. So for the price of a Glock you can get a somewhat upgraded Glock.
      Still only a good plan if you WANT to build one.
      I’ve seen more companies making slides and barrels lately, maybe the price will come down. I’ve got one built and another on the shelf waiting for deals.

  • Donald Blaufuss January 29, 2018, 11:44 am

    Where did you get the slide and what did it cost?

    • Thomas Gomez January 29, 2018, 2:13 pm

      It was the slide off of my Glock 19. You can buy slides from a number of places online.

  • Anthony January 29, 2018, 11:02 am

    By building your polymer 80 are you saving any money than buying a used gun of similar model? Just curious if this is a way to get into a cheaper gun or is it more a way to make a custom non serial number gun. If you saved money compared to used gun, on average how much did you save?

    • Gopher January 29, 2018, 2:53 pm

      Sidenote, will become custom serial number gun for paperwork transfer.

    • Guns2317 January 29, 2018, 4:31 pm

      I don’t think you actually save any money by building it yourself. I did one of these as a Gen1 project shortly after they debuted. I bought an extended 9mm barrel and slide, sights, trigger assembly kit, etc since I did not have any spare Glock parts laying around. It was a fun project, learned a bit, but bottom line the final cost was just about the same for a new Glock. There is a certain satisfaction in going to the range and shooting something you built and tuned for yourself.

      For roughly the same cost as the 80% kit, Lone Wolf had been selling their frames last fall complete with trigger assembly, but you do need to do the regular FFL paperwork to buy one.

      Bottom line, if you are looking to build a “ghost” gun, then the 80% kits are the way to go. Otherwise, you are not really saving much money to do it yourself. When I get some more funds, I will likely buy another kit just for the enjoyment of having built it myself. Probably gonna wait for them to do the .45 frame to do so.

      • Anthony January 30, 2018, 11:17 am

        Thanks for the info. I figured it would not save a lot of money if any at all.

  • GreenWolf70 January 29, 2018, 10:07 am

    The trigger bar tab dragging on the slide, and/or the safety disconnect button not moving smoothly in its hole are probably the most mentioned issues with the Poly80 frames. The rear rails should be flush with the rear tab on the frame. If they are setting too high remove burrs and metal at the bends that prevent the rail from fully seating. Don’t redrill the hole to fit the rear rail, make it sit flush. If your rear rails are sitting too high they also cause the striker bar to sit too high on the trigger bar sear and leave a larger than Glock size gap between slide and frame.

    • Thomas Gomez January 29, 2018, 2:14 pm

      Exactly! Thank you Sir.

  • Paul O. January 29, 2018, 10:04 am

    Thanks for the article. I picked up a P80 kit a little while ago and am still deciding on a slide for it. Looks like paying attention to polishing every contact surface is a good idea.

  • Tom Coats January 29, 2018, 8:16 am

    I own several handguns, including a couple of Glocks, have been a shooter most of my life, and think I understand quite a bit of technical knowledge.
    But I do not understand what you are reporting after buying the kit for refinishing the pistol?
    Does the kit replace the plastic with metal parts?
    Sorry for the density of my brain, but I am lost as to what exactly was accomplished?
    You seem to be skilled at smithing and adjusting the Glock, but I am unsure as to what exactly you accomplished with the kit and your knowledge and skill?
    Tom Coats
    Hot Springs Village, ARK

    • Thomas Gomez January 31, 2018, 1:16 pm

      The kit replaces the lower frame. It was a pet project and for testing I used the slide off of a stock G19. The polymer 80 may turn into a Roland Special type build.

  • NRSNick January 29, 2018, 7:44 am

    Built two, love them. One of the 19 ilk, one 17. The first version of the 17 was a bit tricky because it was first Gen, in which you must hone the rear rails, which are polymer also. It required some special fitting and the slide was sticking for a while, but the 19, which has the inserted metal rear rails, was a breeze. The 17 version has now been upgraded to use the same metal rails in the rear is much easier. Next is a P320 kit that has been much awaited and backorders are swelling for it\’s full release. Both of my pistols are accurate and have better ergos in my opinion. Best of all,…no serial numbers and legal.

    • Guns2317 January 31, 2018, 3:34 pm

      Were you able to buy the rear frame rails block and retrofit it to your Poly 80 Gen 1 kit? I would love to be able to do the same with mine, that would address what I see as a weakness in the first design.

  • NRSNick January 29, 2018, 7:43 am

    Built two, love them. One of the 19 ilk, one 17. The first version of the 17 was a bit tricky because it was first Gen, in which you must hone the rear rails, which are polymer also. It required some special fitting and the slide was sticking for a while, but the 19, which has the inserted metal rear rails, was a breeze. The 17 version has now been upgraded to use the same metal rails in the rear is much easier. Next is a P320 kit that has been much awaited and backorders are swelling for it’s full release. Both of my pistols are accurate and have better ergos in my opinion. Best of all,…no serial numbers and legal.

    • JaegerMeister January 30, 2018, 2:08 pm

      You say the 17 has been upgraded to the metal rear slide. Was this added to the Gen 1 version or did you purchase another Gen 2 polymer? If you upgraded the Gen 1 to the metal rear slide, where did did you purchase the metal rear slide part???


      • NRSNICK January 30, 2018, 7:35 pm

        I didn’t upgrade my Gen 1, I saw the Gen 2 afterwards. I only have the Gen 1, but I’d like to get the 2. I really don’t know if you can retro-fit the Gen 1 with the metal rail piece or not, but I’m sure you can get the answer by calling them. If you can, ask if they’ll sell the rail by itself to do the job. I’d love to know as well.

  • DC January 29, 2018, 7:18 am

    Would u feel comfortable trusting it as your ETC gun? I also noticed that there isn’t as much of gap between the slide and the lower, do u think that’s better than factory on that as well as overall?

    • Thomas Gomez January 31, 2018, 1:22 pm

      Hi DC.
      After all the hand finishing I have done, yes. In regard to quality I would say they are the same. I bought it because of the stippling and large beaver-tail, plus as an armorer I wanted to assess the quality and go through the build process. If you finish one, find a Glock armorer to do a quick assessment. If they okay it, and it will run 100 rounds with no issues, you are probably okay.

  • Jay January 29, 2018, 6:29 am

    These have been out on the market since May of 2016!. Maybe this is just a sales pitch for polymer 80!

    • Jeffrey Beam January 29, 2018, 8:17 am

      No problem with that. Sales pitches are all about providing information. This is the first time I’ve heard of it no matter when it came out so I’m grateful for this kind of article.

    • Jeffrey Beam January 29, 2018, 8:20 am

      Sales pitches are all about providing information. Sine I have never heard of this I am grateful for this article sales pitch or not.

    • Thomas Gomez January 31, 2018, 1:25 pm

      I have no vested interest in Polymer 80. I just saw one at BMC Tactical and thought it looked cool.


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