There are a myriad of reasons to upgrade your Glock pistol slide. Chief among them is red dot compatibility–there are few upgrades you can make to a handgun that will improve your performance as quickly or dramatically as a quality red dot, making it one of our Top 5 Pistol Accuracy Upgrades–but an upgraded slide can also offer lower recoil, faster cyclical times, or other benefits.
Once you’ve decided to make the switch, though, you have to determine how to go about it; do you send your existing slide off to be customized, buy a new one aftermarket, or stick to Glock OEM parts with an MOS slide?
Below, we’ll take a lot at the relative merits of each option and which is best for your pistol.
Understanding Glock Pistols
The first thing you need to know is which slides are compatible with your firearm. For the most part, that’s pretty easy; just find a slide that’s designed for your model and generation, and you’re good to go. However, for certain models, this can be a bit more complicated, since they can utilize not only their own slides, but also those from other models or generations.
Each Glock pistol is assigned a model number. The original, first-generation pistol was the Glock 17, the name of which is often thought to refer to its 17-round capacity, which was quite remarkable in its day. However, this assumption is erroneous, as is made obvious by the fact that the Glock 19 only holds 15 rounds.
The Glock 17 actually takes its name from the fact that it was Gaston Glock’s 17th patent. Thereafter, Glock pistols are numbered progressively, with each new pistol being assigned the next available number. However, not all pistols are brought to market, and not all those that are brought to market are available in the US, so there are a few numerical gaps in the catalog.
Most pistols are limited to other slides of their same model, but full-sized Glocks, such as the 17, can also utilize slides from other models built on a full-size frame of the same (or sometimes similar) caliber. So, a Glock 17 could be fitted with a 34 or 17L slide, so long as the appropriate barrel is used. Since 9mm and .40 S&W handguns also share a frame, a Glock 17 could utilize a Glock 22 slide and barrel.
Similarly, certain models such as the G45 and G19x can accept slides from other compact handguns, such as the ubiquitous Glock 19, even though they use different frame sizes.
However, it is important to maintain generational compatibility. A Glock 19 Gen 5 slide will not function properly on a 3rd or 4th general pistol, and vice versa. Some Gen 3 and 4 slides are compatible with either generation frame, but it’s wise to check before ordering.
Upgrading Your Glock Slide
If your pistols already shoots just fine (and of course it does—it’s a Glock) you may be wondering why you should bother upgrading at all. There are several good reasons, but the most common is red dot compatibility.
Red dots and mini reflex sights offer a wide range of benefits, which we’ve covered in depth in our article on Pistol Sights 101. However, many older pistols are not designed for them, and as such require either modification to or replacement of the slide in order to make your pistol red dot ready.
Aftermarket or custom slides can also reduce weight compared to OEM models. This weight reduction generally isn’t enough to make a noticeable difference when carrying the firearm but can influence the way it operates.
A lighter slide, in conjunction with proper tuning of the major springs, can result in less reciprocating weight, reducing felt recoil. It can also increase cyclical speed, allowing for slightly faster follow-up shots. Neither of these improvements is likely to be drastic, but even a slight improvement in either area can lend an advantage, which is why these sorts of upgrades are common in competition circuits.
Many users, though, opt for a new slide simply to improve the aesthetics of their firearm. Replacing a major component such as a slide can offer a new look to an old firearm, in addition to the more practical advantages.
In most cases, replacing a Glock slide is a very straightforward modification. At most, replacing a slide will require detail stripping the old slide, a process that we cover in-depth in our article on How to Detail Strip a Glock. This procedure requires nothing more than a Glock tool or small punch and a sight pusher or non-marring hammer to accomplish. If you’re averse to working on your firearm, though, you can also turn to your local gunsmith or Glock armorer.
Or, in some cases, installation may be as simple as field-stripping your pistol–a process every Glock owner should be comfortable with.
Whether or not your slide replacement will require tools will depend on whether you opt for a stripped or complete slide. A stripped slide will include only the slide itself, while a complete one will already have all of the small parts installed. A complete slide will only require you to drop in your barrel and guide rod assembly, no different than reassembling your Glock after cleaning it.
Regardless of whether you choose a stripped or complete slide, you won’t have to worry about getting an FFL involved. With Glock pistols, the frame is the serialized and regulated component, so a new slide can be ordered online, shipped to your door, and installed without any paperwork required, making it one of our Top 8 Glock Pistol Upgrades.
Glock-compatible slides can be grouped into three major types: aftermarket, custom, and Glock MOS.
Aftermarket Slides
Aftermarket slides are those designed for Glock pistols, but manufactured by a third party. Zaffiri Precision and Strike Industries both offer this manner of slide, offering drop-in compatibility, optics cuts, and more.
These slides vary widely in design and function. They can offer reduced weight, more aggressive serrations, or additional window cuts for use with ported barrels.
In the case of red dot compatibility, many aftermarket slides are cut for a specific dot or pattern. This offers the simplest mounting configuration, allowing you to bolt your optic directly to your slide, but limits you to a single optic or footprint. However, by eliminating the need for an adapter plate, these slides also eliminate a potential failure point, namely the attachment of your plate to your pistol.
Directly milling a slide for a specific optic also typically allows for a stronger connection, since the bolts can be run through the optic and into the full depth allowed by the slide, rather than being limited by the thickness of the optic plate.
The lack of need for an adapter plate also allows your red dot to sit slightly lower, which may reduce the height required for your iron sights to be able to cowitness.
Unfortunately, because you’re buying an entirely new slide, aftermarket slides are often more expensive than sending your existing slide to be milled. They are also not Glock parts, and as such are not covered by Glock under warranty.
Custom Slides
Custom slides are those that were once original and OEM, but have been modified by a third party. Some popular customizers include Taran Tactical Innovations and Agency Arms.
With these slides, the sky is the limit. A custom shop can offer a huge range of lightening cuts, optics options, serrations, aesthetic modifications, and more. Unlike aftermarket slides, you’re often able to mix and match individual modifications or packages as well, allowing you to build the precise slide that you desire.
Like aftermarket slides, many custom services can offer direct milling of your slide for a specific optic, negating the need for an adapter plate. If you prefer the versatility of a more adaptable system, though, some makers do offer universal cuts that utilize plates, such as Agency Arms’ AOS system.
While often cheaper than buying a completely new slide–particularly if you are only getting your slide milled for an optic, rather than choosing a bunch of add-ons and upgrades–slide customization services can at times match or even exceed the price of a new slide. But, for many, the level of control that you receive over the exact details of your slide is worth the cost.
Custom slides may also incur a wait time, while the other options on this list do not. Because you are sending your existing slide off to be machined, your firearm will be out of commission until it returns, which can be anywhere from a few weeks to multiple months. Dropping in a new slide, on the other hand, takes only a few minutes.
Glock MOS Slide
The only true Glock slide on our list, Glock MOS slides are an excellent option for those who want to stick to OEM parts for their pistol or are concerned about voiding their warranty. While aftermarket slides may be Glock-compatible, they’ll never be truly Glock. An OEM MOS slide, on the other hand, is every bit as authentic as the one that came on your pistol.
Glock’s MOS system sets the bar for adaptable optics cuts. It’s versatile enough to fit most of the red dot and mini reflex sight footprints on the market with the appropriate adapter plate and sits low enough that a cowitness can be achieved with most optics with standard suppressor-height sights.
Still, the system does require an adapter plate–as do all non-specific optic cuts. The presence of a plate means another set of screws that could back out or come loose and limits how deeply your optics screws can be attached to your firearm.
By choosing a Glock MOS slide and having it installed by a Glock-certified armorer, though, you can maintain your factory warranty and be assured of fit and function.
Conclusion
A new slide is a great way to spruce up an old firearm, whether with an aesthetic upgrade, improved recoil profile, or a new modern optic. Whether you opt to send off your existing slide for some custom porting, drop in a slick new aftermarket model, or stick to the original with a Glock MOS slide, you’ll be happy with the boost in performance offered by your new upgrade.
Of course, if you’re looking for a more comprehensive look at upgrading multiple facets of your pistol, we can help with that too. Check out our article on How Common Mods Actually Affect Your Pistol for more information.
