The upgrade that matters most on a .40 S&W Glock 22 or 23 is a 9mm conversion barrel: a drop-in part that lets you shoot cheaper 9mm on the same frame. Then the standard Glock stack: optic cut, trigger, sights, light, and mags.
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The Glock 22 and Glock 23 are the .40 S&W duty Glocks that armed American police for two decades, and the resulting wave of law-enforcement trade-ins makes them one of the cheapest ways to buy a proven, duty-tested Glock today. The most valuable upgrade for either gun is a 9mm conversion barrel: a single drop-in part that lets the .40 frame shoot far cheaper 9mm. After that, the G22 and G23 run the exact same aftermarket stack as their 9mm siblings, triggers, sights, lights, and optics. For the broader Glock barrel picture, see our best Glock barrels guide, and for the 9mm sibling path, the Glock 19 upgrades guide.
Buy in this order. The 9mm conversion barrel is the upgrade that changes how much it costs to feed the gun, so it leads. Spare factory magazines come next because they are the cheapest reliability insurance on any duty pistol. Trigger, sights, and a light follow, and a milled-slide red dot is the last and most expensive step on a .40 G22 or G23.
| Priority | Upgrade | Cost | Impact |
|---|---|---|---|
| 1 | 9mm Conversion Barrel | $110-$135 | Shoot cheaper, softer-recoiling 9mm on the .40 frame |
| 2 | Spare Magazines | $25-$40 each | Cheapest reliability and training-volume upgrade |
| 3 | Trigger | ~$100 | Flat-face drop-in cleans up the mushy factory pull |
| 4 | Sights | $45-$90 | Fiber-optic for daylight speed, suppressor-height for a red dot |
| 5 | Weapon Light | ~$184 | Target ID in low light on the full-length rail |
| 6 | Red Dot (+ slide milling) | $310 + milling | Faster acquisition once the slide is optic-cut or you run MOS |
Key insight: The standard .40 G22 and G23 slide is not optic-cut from the factory. Budget for slide milling or a MOS slide before you buy the red dot, and do not assume a 9mm Gen3 optic-ready slide built for the G17 or G19 will drop onto the wider .40 G22 frame, it will not. If you only want one upgrade, make it the conversion barrel.
The best upgrade for a .40 S&W Glock 22 or 23 is a 9mm conversion barrel, a drop-in part that lets the gun fire cheaper, softer-recoiling 9mm without touching the frame or slide. The Lone Wolf AlphaWolf AW-229N ($134.95) handles the full-size G22 and G31; the Lone Wolf LWD-239N ($109.95) handles the compact G23 and G32. Both are stress-relieved 416 stainless, install in minutes with no gunsmithing, and keep the factory barrel length so your existing holster still fits.
The magazine catch: a conversion barrel does not make your .40 magazines feed 9mm. The cartridges are different diameters, so you run the converted gun on standard 9mm Glock magazines, G17 mags behind the AW-229N and G19 mags behind the LWD-239N. Buy a set of 9mm mags alongside the barrel. On Gen4 guns, a dedicated 9mm recoil spring smooths out cycling; Gen3 guns usually run the conversion on the factory spring. The non-threaded barrels here are the right pick for most shooters; suppressor and compensator users want the separate threaded SKU instead.
Premium match-grade options like KKM exist at a higher price, but the Lone Wolf barrels are the verified, widely stocked, best-value pick and the reason most people convert a .40 Glock in the first place. Where these barrels sit in the wider Glock barrel lineup, including threaded and match options, is covered in the best Glock barrels guide.
The two conversion barrels lead because they change what the gun costs to shoot. Below them is the standard Glock upgrade stack, a trigger, two sight options, and a light, each one a true drop-in that fits the Gen 3/4 .40 frame the G22 and G23 are built on. The red dot ranks where it does because it carries a slide-milling cost the rest of the list does not.
Best upgrade overall, shoot cheap 9mm on a .40 G22
Best 9mm conversion for the compact Glock 23
Best red dot once the slide is milled or on a MOS slide
Best trigger upgrade
Best iron sights for a non-optic G22/G23
Best sights for a red-dot or threaded-barrel build
Best weapon light for a duty G22
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The best trigger upgrade for the G22 and G23 is the Overwatch Precision DAT flat-face shoe (about $100). It squares up the press and cuts the pre-travel that makes the factory Glock trigger feel vague, and because the G22 and G23 share the full-size Gen 3/4 trigger group, the same DAT fits both guns and clears every Glock holster. For the full cross-model Glock trigger ranking behind this pick, see our best Glock triggers guide.
Pick your sight by what the gun is for. If the G22 or G23 stays iron-sighted, the Dawson Precision fiber-optic set ($88.95) pulls your eye to the front sight fast in daylight and is a real upgrade over the factory plastic sights. If you are mounting a red dot or running a threaded conversion barrel with a suppressor, the AmeriGlo GL-429 suppressor-height steel sights ($45.99) sit tall enough to co-witness through the optic and clear a can. Buy one or the other based on the build, not both.
The Streamlight TLR-1 HL ($183.99) is the right weapon light for a duty G22. Its 1,000 lumens and 20,000 candela throw far enough to identify a threat in a dark room, it mounts to the full-length G22 accessory rail, and it has the broadest duty-holster support of any pistol light. On the shorter G23 dust cover the full-size TLR-1 footprint can overhang slightly, so confirm holster fit before you commit.
A red dot is the last upgrade, not because it is unimportant but because the .40 G22 and G23 slide is not optic-cut from the factory. Once you have milled the slide for an RMR footprint or bought a MOS-cut slide, the Holosun 507C X2 (about $230) is the best-value dot: multi-reticle, solar failsafe, and a side-loading battery. Pair it with the AmeriGlo suppressor-height sights above for a lower-third co-witness.
Why magazines come first: magazines are the cheapest reliability and training-volume upgrade you can buy, and they are the part most likely to be tired on a police trade-in G22 or G23. The factory Glock 22/35 .40 S&W 15-round magazine ($39.49) is the workhorse: it runs in the full-size G22 and long-slide G35, drops into the compact G23, and even feeds the subcompact G27 with grip overhang. Build a stack of these before you spend on any other category.
How many you need: for everyday carry, three magazines is a reasonable floor, one in the gun and two spares. For range training and classes, six to eight keeps you shooting instead of reloading, and it lets you rotate springs and track wear by magazine. A duty or home-defense rig should hold at least six on hand.
The conversion-barrel gotcha: these are .40 S&W magazines. A 9mm conversion barrel does not let them feed 9mm; .40 and 9mm Glock magazines are not interchangeable. If you convert the gun to 9mm, you also buy a set of 9mm Glock magazines, G17 mags for a converted G22 and G19 mags for a converted G23.
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Best Glock Barrels 2026 - Where the .40-to-9mm conversion barrels fit in the broader Glock barrel lineup, including threaded and match-grade options.
Best Glock Triggers 2026 - The full cross-model Glock trigger ranking behind the Overwatch DAT pick in this guide.
Best Glock 19 Upgrades 2026 - The 9mm sibling platform with the same upgrade stack, useful if you also run a 9mm Glock alongside the .40 G22/G23.
Best Pistol Lights 2026 - Weapon-light alternatives to the Streamlight TLR-1 HL across compact and full-size footprints.
Best Glock 26 Upgrades 2026 - The subcompact Glock upgrade path; the .40 G27 is the subcompact sibling that shares this guide's 15-round magazine.
Weapon light, red dot, spare mag, and trigger, the upgrades most pistol owners add first.
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Avid shooter with 9+ years of experience including competition shooting. Built 10+ AR-pattern rifles and several handgun platforms for home defense, competition, and suppressed night shooting.
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