Slimline Glock Optics Screw Jam – How to Fix It

Slimline Glock models are increasingly popular for both concealed and open-carry with aftermarket precision optics installed. Featuring a height and length similar to some of the maker’s most popular compact and subcompact models, they feature slimmer width thanks to a single-stack magazine. The result is a gun that’s easier to handle for shooters with smaller hands while also providing less bulk to conceal under clothing. While these thinner Glocks offer the same reliability and industry-leading features Gaston’s G series has become known for, some shooters have encountered problems once they tighten down the Glock MOS screws and take their pistol to the range with a new optic installed.

Maximum Impact from a Minimized Footprint

As an example, the G19 is a great gun, but it can be a lot to handle for some shooters. The G48 is a Glock Slimline version that shares the same length and height, giving it a familiar feel for many shooters, but with a single stack magazine well that keeps the width of the weapon down to only 28mm at its widest point. This allows for increased finger wrap that gives a stronger one or two-handed grip for those with short fingers, smaller bone structures in their hands or wrists, or who suffer from a weaker grip due to age or injury. Glock’s Slimline engineers do more than just put your frame on a diet, however.

The slide of the Slimline models has been similarly shaved down to give it better balance and support on the thinner frame. You still have all the features you’d want on your pistol, but packing them all into less real estate means some of the internal workings of your gun have been packed in more closely. While Glock’s QA department ensures your pistol is reliable out of the box, some Glock Slimline shooters have noticed that reliability takes a hit after installing a premium sight to the pre-milled mount pattern on top of their slide with standard Glock MOS screws.

While shooting, a failure to extract can occur, with the spent cartridge casing failing to clear the ejection port of the weapon. The next round doesn’t have the space to chamber, instead often either jamming in the gun or stovepiping, hanging out of the jammed ejector port after finally pushing the spent case up and out of the way. Standard practice is to remove the magazine, rack the slide to clear the jam, reinsert the magazine, give it a tap to seat it, and then rack the slide again to load the new cartridge. A single occurrence can be an aberration as you “break in” your weapon, but repeated failures could point to a far bigger issue that needs to be addressed to avoid damaging your weapon. 

Don’t Let a Screw Jam Screw Up Your Range Time

While some are concerned that the weight or size of their new optic is somehow interfering with their weapon’s reliable cycling, rest assured your Glock Slimline is more than capable of handling a fully featured modern reflex sight. As Mike shows in our companion video, the problem has to do with your right mounting screw and how friendly your slide’s internal parts and the factory milling parameters had to get to shrink the width of your weapon down to a little wider than a brand-new deck of cards. The right-hand Glock MOS screw channel opens directly into the same channel your extractor rod moves through as the weapon cycles.

If the Glock MOS screws are long enough to enter the same space as the extractor rod, it can’t make full use of the recoil forces that drive it, and the spent shell may not clear the weapon’s port. On the inside of the weapon, every round fired can scrape the extractor rod along the surface of the screw, scoring it and causing damage that can take a cumulative toll on the weapon. Backing the screw off, however, leaves your Glock Slimline optic without a stable base, destroying your accuracy while potentially allowing dirt, moisture, and movement to begin damaging the mounting surface of either the weapon, the optic, or both.

Fixing A Glock Slimline Optic Screw Jam

You can fix your Glock Slimline optic screw jamming issues with only a slight modification of one of your Glock MOS screws. This simple at-home customization takes a minimum amount of tools, a little bit of work, and a few short minutes of your time. 

1. Make Sure Your Gun is Unloaded and Made Safe – Remember that every gun is loaded until proven otherwise. Check and double-check your weapon to prevent accidents.
2. Gather Your Tools – You’ll need an appropriate driver or wrench to remove your right optic screw, some blue thread locker for reassembly, and either a belt sander or rotary tool with a sanding bit. While you can use a small file or rasp in a pinch, the process will be longer, and you’ll need to take greater care to avoid metal burrs marring the threading from low-speed, high-friction material removal. Don’t forget the protective gear you need to keep your eyes, ears, and fingers safe.
3. Remove the Right Glock MOS Screw – Using your driver or wrench, remove the right screw. Some gun owners find it easier to remove their slide first, letting them set the frame aside while they place the slide flat to work on it.
4. Work Carefully to Remove Material From the End of the Screw – It’s important to understand that you are making a small adjustment to the length of the screw. In our example video, Mike identified the usable thread length for his Glock Slimline optic screws started at 8.6mm, and 8mm was the final useable thread length–a difference of just over a half millimeter or about two revolutions of threading.
5. Apply Some Thread Locker and Reinstall Your Optic Screw –  Put a small amount of thread locker on the modified screw and reinstall it, tightening it to around 10-15 inch-pounds of force–for reference, that’s when it stops wanting to turn and before you start cranking on it to force it into place. If possible, let the thread locker cure per manufacturer instructions or overnight.
6. Rezero Your Optic – Anytime you remove or partially unmount your optic, it’s a good idea to verify it’s still zeroed in. Take your Glock Slimline out to the range and get some rounds in.

Precision Reflex Optics

As leaders in high-performance optics, we’re proud to offer the tips and tricks you need to improve accuracy and precision at the range, in the line of duty, or when carrying. Our line of red dot sights features industry-leading technology, like shake-to-awake power-saving modes, adjustable brightness, and durability you can count on without breaking the bank. Get the reflex sight your Glock Slimline needs for better shooting from Gideon Optics today.