Fix My Glock

My Glock doesn't Glock! Help!

Work In Progress

Glock clones are enticing builds for beginners. There are lots of reasons but some of the top are:

• the Glock itself is one of the most widely known handgun designs in the world
• the design uses relatively few parts
• the non-printed parts are widely available in the US
• the frames are relatively easy to print

Despite the brilliant simplicity of the design, it's still a precision machine that relies on well made parts, correct assembly, and maintenance of precise tolerances. Beginners expecting a "cookbook" build often find themselves with a malfunctioning gun and no idea how to fix it. This guide

Troubleshooting Your Print

Coming soon.

Troubleshooting Your Build

Functional Testing

WARNING: DO NOT FUNCTIONAL TEST WITH LIVE AMMO. FUNCTIONAL TEST EMPTY OR WITH DUMMY ROUNDS ONLY!!!

If you do not have dummy rounds, you can print some: https://odysee.com/@spaceboundtactical:9/SnapCaps-Dummy-Rounds:9 . These won't function quite as well as commercial dummy rounds (a.k.a. snap caps) but they're good enough to get through most functional tests.

You're going to start with your frame and slide completely disassembled, so it's best to go through these tests as you do your initial assembly. If your gun is already assembled, take it apart so you're starting from scratch. Complete disassembly is easy and good practice.

1. Insert the front rail (not mounted in the frame) into the slide and check that it moves freely all the way to the front. Remove it from the slide.
2. Insert the rear rail (not mounted in the frame) into the slide and check that it moves freely up to the ejection port. Remove it from the slide.
3. Install (only) front and rear rails and locking block into the frame. Mount the slide to the rails and verify that you can move it all the way to the rear and back to the front with almost no resistance. Remove the slide.
4. Install the slide lock (bar in front of the locking block) with its spring. Mount the slide to the rails and verify that it still moves without resistance. Remove the slide.
5. Install the barrel and recoil spring assembly (recoil spring and guide rod) in the slide. Mount the slide to the rails and verify that it "catches" on the slide lock bar and will not move forward beyond that point.
6. Pull the slide to the rear and verify the only resistance is the force of the recoil spring. Remove the slide.
7. Remove the rear rails and the two locking block pins. Install the complete trigger assembly with rear rail, slide release, and locking block pins.
8. Mount the slide to the rails and verify that it moves as it did in the previous check. Make sure it does not hit the ejector or trigger block. Remove the slide.
9. Install the firing pin assembly (firing pin, firing pin spring, spring cups, spacer) in the slide and install the backplate to hold it in place. Do not install the firing pin safety, extractor, or extractor spring assembly yet.
10. Mount the slide to the rails. Pull the slide all the way to the rear, then ease it forward into battery. Verify that the trigger "resets" and moves all the way forward. Partly retract the slide and verify the chamber is empty (no dummy round and definitely no live round). Ease the slide back into battery.
11. Pressing only on the edge of the trigger (to avoid depressing the trigger safety lever) gently depress the trigger. You should feel and see the trigger safety lever catch on the frame and prevent any further rearward trigger movement. Repeat this test pressing from different angles and with different amounts of force until you are confident that the trigger will not move fully rearward unless the trigger safety lever is also depressed.
12. Pressing on the trigger such that the trigger safety lever is depressed, gently depress the trigger until you feel it meet resistance. Release the trigger and verify it moves freely back to the forward position.
13. Pressing on the trigger such that the trigger safety lever is depressed, gently depress the trigger until you feel it meet resistance. Gradually apply additional force until the trigger "breaks" and releases the firing pin. You will hear and feel the firing pin release. Release the trigger and verify it remains in the rearward position.
14. Pressing on the trigger such that the trigger safety lever is depressed, hold the trigger in the rearward position while you pull the slide all the way to the rear. Ease the slide all the way forward while still holding the trigger to the rear. Gradually ease the trigger forward. Part way through it's travel you should feel (and hear) a "click" as the trigger resets.
15. Pull the trigger until the firing pin releases. Release the trigger and cycle the slide. Verify that the trigger resets and moves all the way forward. Pull the trigger again and verify the firing pin releases. Repeat this test 5 - 10 times.
16. Remove the slide. Remove the slide backplate. Install the firing pin safety plunger and spring, ejector, and ejector spring assembly. Reinstall the slide backplate.
17. Mount the slide and repeat the trigger functional tests. Remove the slide.
18. Install the magazine release and magazine release spring in the frame. Without mounting the slide, insert an empty magazine into the magwell. Verify the magazine locks in place. Pull firmly on the magazine and verify that the magazine release holds it firmly in place. If you can pull out the magazine without depressing the magazine release, it will likely release when firing the gun and you'll experience miss-feeds or a complete drop.
19. Press the magazine release and verify that the magazine can be easily removed. It need not drop free (especially empty), but it should not take much force to remove it.
20. Mount the slide and repeat the magazine retention and release tests.
21. Pull the slide all the way to the rear and verify that the empty magazine causes the slide release lever to engage and lock the slide back.
22. Press the slide release lever and verify that the slide snaps forward quickly and firmly under the force of the recoil spring.
23. Pull the slide all the way to the rear so it locks back on the empty magazine. Press the magazine release and remove the magazine. Verify the slide remains locked back.
24. Load the magazine with two or more dummy rounds. Insert the loaded (dummy rounds only) magazine and verify that it locks in place and the slide does not release.
25. Release the slide by pulling back until the slide release disengages and then let go. Verify the slide fully returns to battery. Verify the position of the extractor indicates a dummy round in the chamber. Pull the slide rearward 1/8 inch (3 mm) and visually verify a dummy round is in the chamber.
26. Remove the magazine. Forcefully pull the slide all the way to the rear and verify the dummy round is extracted and ejected.
27. Insert the magazine (with at least two remaining dummy rounds). Pull the slide all the way to the rear and release. Verify the slide fully returns to battery and that a dummy round is chambered.
28. Forcefully pull the slide all the way to the rear and verify the dummy round is extracted and ejected. Release the slide and verify the slide fully returns to batter and that another dummy round is chambered. Repeat until all dummy rounds in the magazine have been cycled and the slide locks back on the empty magazine.

Troubleshooting Failures

• Watch this video to better understand how the parts in the gun are supposed to function: https://youtu.be/y2fMRqFEEZI
• Print an Armorer's Backplate (https://www.thingiverse.com/thing:3591065) so you can actually see what's going on with the trigger mechanism. This is particularly useful for troubleshooting firing pin engagement and trigger reset issues. WARNING: NEVER FIRE LIVE-AMMUNITION WITH AN ARMORERS BACKPLATE INSTALLED!

Live-Fire Testing

WARNING: DO NOT LIVE-FIRE A GUN THAT FAILS ONE OR MORE FUNCTIONAL TESTS! Live ammo will not fix functional problems and shooting live ammo in a gun with known issues can put yourself and others at risk of serious injury or death.

WARNING: WEAR EYE PROTECTION AND EAR PROTECTION AND KEEP THE GUN POINTED IN A SAFE DIRECTION AT ALL TIMES! Accidental discharge is always possible with an unproven build. Additional Personal Protective Equipment (PPE) such as protective gloves, heavy long-sleeve shirts/jackets, etc. is always recommended. Use of a mounting system that allows the shooter to fire the gun without any physical contact is ideal, however untested make-shift mounts may actually be more dangerous than firing by hand.

1. Manually lock the slide in the rearward position using the slide release. Remove the magazine (if inserted).
2. Load one round only into the magazine. Insert the magazine and verify it locks in place. Release the slide and verify the slide fully returns to battery and that the live round is chambered.
3. If not using a mount, hold the gun firmly in your dominant hand, finger off the trigger, waist high and slightly canted so no body part is directly behind the slide.
4. Verify that the general direction of aim will not overshoot your backstop, nor impact the ground close to you. You do not need to try to aim with the sights to hit a specific target, just verify a safe trajectory.
5. Squeeze the trigger until the firing pin releases and fires the round. Verify the slide locks back on the empty magazine.
6. Remove the magazine. Release and remove the slide. Inspect the frame carefully (magnification is recommended) and verify there are no cracks or other damage. Pay particular attention to the areas around the locking block and the magazine release.
7. Repeat the single round test 10 - 20 times, inspecting after each shot. If any frame damage is observed, stop immediately. If there are any failures (failure to fire, failure to feed, failure to eject, etc.) stop immediately and troubleshoot using dummy rounds. If testing is successful to this point, it should be safe to fire aimed shots from a normal stance in subsequent tests.

Common Problems

Light Primer Strikes

Symptom: Firing pin releases when trigger is pulled but round does not fire. Inspecting the round shows no mark or a shallow dent in the primer.

Common Cause: Firing pin is hitting the firing pin safety plunger. The plunger should be depressed by the "shark fin" extension on the trigger bar. Poor slide fit can cause this. If the slide is sitting too high due to rails being too high in the frame or rails being too loose in the slide or frame, the plunger may not be depressed far enough to clear the firing pin. Out-of-spec non-OEM parts found in cheap parts kits can also contribute to this problem.

Failure to Return to Battery

Symptom: After firing a round, the slide stops short of the full forward position. Trigger is reset, but pulling it either doesn't release the firing pin, or firing pin is released but round does not fire. Inspection of the round may show an off-center light primer strike mark.

Common Cause: Too much resistance in the slide movement. Recoil spring does not have enough energy to overcome the resistance and complete the last part of travel to lock the barrel in place. Perform the steps in the Functional Testing section to determine and correct the source of the resistance.

Trigger Won't Release

Symptom: Pulling trigger all the way to the rear doesn't release the firing pin.

Common Cause: Trigger housing is loose in the frame. If the trigger housing can rock forward and back, it can prevent the cruciform from moving down far enough to release the firing pin. It's often possible to use a thin piece of plastic as a shim between the front of the trigger housing block and the printed frame. Create and print a shim in your slicer or simply cut a small strip from an old credit card, plastic blister packaging, etc. You can dry-fire test with the shim just slid in place to verify it corrects the problem. If it does, use some "super glue" to permanently fix the shim to the frame.

Possible Cause: Cheap Lower Parts Kits (LPKs) may have poorly made and/or out-of-spec parts. This is particularly common with trigger parts since most parts are stamped instead of machined. Use an Armorer's Backplate to observe the cruciform engagement of the firing pin. If there is too much engagement, it may be possible to correct by bending the cruciform. Do this only as a last resort when all other probable causes have been ruled out. If you do this, you must use an Armorer's Backplate to verify that you still have sufficient firing pin engagement. Insufficient cruciform to firing pin engagement is unsafe and can lead to uncommanded discharges when the gun is dropped or even roughly handled.

Trigger Won't Reset

Symptom: Dead trigger (trigger remains in the rearward position) after firing a round.

Common Cause: When the slide returns forward it pushes the trigger connector to the left allowing the trigger bar to move upward under spring tension. Interference between the trigger bar and the frame can prevent this upward movement (which will keep the the firing pin from catching on the cruiciform). Verify the trigger bar can move freely without interference from the frame.

Possible Cause: Cheap Lower Parts Kits (LPKs) may have poorly made and/or out-of-spec parts. This is particularly common with trigger parts since most parts are stamped instead of machined. Use an Armorer's Backplate to observe the trigger reset in dry-fire. If connector does not move far enough to release the trigger bar, consider replacing the trigger parts with genuine Glock parts.

Asking For Help

The amount of help you can expect depends on how much information you provide. If you're going to ask for help, provide as much of the following info as you can:

Build Info

• Type of frame you printed (i.e. which rails does it use: FMDA, PY2A, P80, Dagger, etc.)
• Specific design you printed (e.g. Chairman Won, Unseen Killer, Broken Bullets, etc.)
• Type of Glock slide in use (17L, 17, 19, 26, 43/48, etc.)
• Brand/model of slide in use
• Rail supplier
• OEM (Glock) or aftermarket Lower Parts Kit (LPK)
• OEM (Glock) or aftermarket Upper Parts Kit (UPK) if you used a bare slide

Print Info

• Filament used (type and brand)
• Nozzle temperature
• Number of walls
• Type and percentage infill
• Chamber? (none, open, closed)
• Filament drying before print
• Any post-processing (annealing, moisture-conditioning, etc.)
• Print orientation (rails-up or rails-down)
• Print angle (relative to horizontal)

Function Info

• Which tests in the Function (dummy round) Test section passed?
• Which tests in the Live-Fire Test section passed?
• What brand and bullet weight ammo did you live-fire test with?
• What behavior do you see on the failing test(s)?

Photos/Video

• Detailed photos showing the isolated problem area
• Photos of the inside of the frame with the slide removed
• Video of the failure if it shows something happening
• Not usually useful: photos of the fully assembled gun, photos without explanation/context, video of you racking the slide and/or pulling the trigger a dozen times in rapid succession (save the rapid hand movements for other things)