The Glock 31 is a full-size .357 SIG pistol built on Glock's large-frame platform—the same general frame family as the G17 and G22. It ships with a 4.49-inch barrel and 15-round standard magazine capacity, and its .357 SIG chambering delivers significantly higher velocity than standard 9mm from an equivalent barrel length.
Glock has discontinued the G31, but a mature and well-supported aftermarket continues to serve the large installed base of Gen3 and Gen4 owners who carry or train with the platform.
Accessory selection for the G31 benefits from its frame-family compatibility with the G17 and G22. Holsters, lights, sights, and most frame-level parts that fit the large-frame Glock family will often fit the G31—but generation matters.
Glock's own duty holster listings explicitly distinguish Gen3/4 from Gen5, and some accessories list G17/G22/G31 compatibility together while others are generation-specific. Verify generation before purchasing anything listed for the Glock large-frame family broadly.
The G31's .357 SIG chambering is its most important accessory compatibility distinction: magazines are caliber-specific. The G22-frame relationship means some .40 S&W magazine bodies are dimensionally similar, but feeding geometry differs and cross-caliber magazine use is not recommended without testing.
Holsters for the Glock 31
Finding the right Glock 31 holster starts with knowing your generation and carry configuration. The G31 shares frame dimensions with the G17 and G22, so many holster makers list all three together—but light-bearing configurations require the exact light model listed, and Gen3/4 shells are not always the same as Gen5.
IWB Holsters
The G31's full-size frame makes IWB carry demanding but achievable for larger-framed carriers or in cold-weather clothing. Strong-side hip at 3–4 o'clock with adjustable cant and ride height keeps the pistol stable and accessible. A Glock 31 holster with full trigger guard coverage is the baseline requirement for any IWB configuration.
OWB Paddle Holsters
Paddle holsters suit range sessions and open carry transitions. The G31's frame profile seats cleanly in any large-frame Glock OWB paddle shell confirmed for the G31 or G17/G22/G31 family. Verify light clearance if running a WML.
Belt Holsters
OWB belt-loop holsters thread directly onto a gun belt for maximum positional stability. Better suited for open carry and duty-adjacent use than deep concealment. Fixed attachment resists shift under the G31's loaded weight throughout sustained activity.
Appendix Holsters
AIWB carry with the G31 is body-type dependent given the full-size grip length. More practical in cold-weather clothing with a substantial cover garment. A claw or wing attachment reduces grip printing at the waistband.
Hook & Loop Holsters
Hook-and-loop mounting suits belly band systems and modular carry panels for beltless carry. Useful in athletic wear, dress clothing, or medical contexts. Confirm the holster pocket is sized for the G31's large-frame width.
Chest Holsters
Chest rigs keep the G31 accessible in field and backcountry roles where hip carry conflicts with pack waist belts. The G31's .357 SIG velocity and 15-round capacity make it a capable backcountry sidearm in a chest-carried configuration.
Sights for the Glock 31
Factory G31 sights are polymer three-dot units—functional at the factory but not appropriate for a pistol in active duty or defensive carry service. Metal sights with tritium capability are the standard upgrade for any G31 used beyond infrequent range sessions.
The G31 uses the same sight dimensions as other large-frame Glocks, so the full Glock large-frame sight ecosystem applies.
Night Sights
Trijicon HD is the most widely recommended night sight upgrade for the G31 platform. The large tritium front dot with a photoluminescent orange outline provides both daylight acquisition speed and low-light tritium performance in a single unit.
The HD XR variant uses a smaller, more precise tritium dot for shooters who prioritize accuracy at distance over maximum close-range acquisition speed—a meaningful consideration on a pistol used for .357 SIG's longer-range capability.
Ameriglo produces night sight sets specifically listed for Glock large-frame pistols including the G31. Their DEFOOR 2 and OPERATOR sets offer front/rear tritium configurations at different height and width profiles for specific carry and duty applications.
Meprolight and XS Sights both produce Glock-compatible tritium options.
XS's DXT2 big dot express sight is the fastest close-range acquisition option in the Glock sight market—it trades long-range precision for extremely fast threat acquisition at typical defensive distances.
Steel Sights for Range and Training
For a G31 used primarily at the range where low-light performance is not a priority, quality steel three-dot or target sights from Warren Tactical, Dawson Precision, or similar makers provide a significant upgrade over factory polymer sights in durability and sight picture consistency.
Steel sights resist the chipping and distortion that factory polymer sights develop under sustained use or holster wear.
Optic Integration
The G31 does not ship with a factory optic cut. Red dot integration requires either slide milling by a gunsmith or a rear sight dovetail mount.
For a legacy duty pistol like the G31, gunsmith slide milling is the cleaner long-term solution. Dovetail adapters work but add height over bore that changes the sight picture geometry.
For G31 owners who want a red dot, Zev Technologies, Agency Arms, and Glock-experienced gunsmiths can mill the G31 slide for common footprints including RMR, DeltaPoint Pro, and Shield RMSc.
Confirm the gunsmith has specific experience with the G31's large-frame slide before committing to a milling service.
Sight Installation Notes
The G31's rear sight uses the standard Glock large-frame dovetail. A quality sight pusher—MGW Sight-Pro or Brownells Universal Sight Tool with appropriate shoe plates—handles rear sight replacement.
Front sight replacement uses the standard Glock front sight tool in 3/16-inch wrench size.
Torque the front sight screw to the manufacturer's specification and apply blue thread-locker to prevent backing out under .357 SIG's recoil impulse.
Lights and Lasers for the Glock 31
The G31's accessory rail is Glock's proprietary rail pattern—not a standard MIL-STD-1913 Picatinny rail. This is the most common fitment mistake for G31 light buyers.
A weapon light must be explicitly confirmed for Glock rail geometry, not just listed as "Picatinny compatible." Many lights use a dual-key system where the Glock-specific key is required for correct seating and retention.
Weapon-Mounted Lights
The Streamlight TLR-1 HL and TLR-7A both include Glock-specific mounting keys in their packaging. Both are confirmed fits for the G31's proprietary rail.
The TLR-1 HL at 1,000 lumens is the home defense and duty specification—broad flood beam, proven duty-grade construction, and near-universal holster maker support in the large-frame Glock market.
The TLR-7A at 500 lumens maintains a more compact footprint for carry-configured G31 setups.
SureFire X300U-B uses the standard SureFire rail mounting system compatible with Glock's proprietary rail through the appropriate mounting key.
At 1,000 lumens with the most comprehensive duty holster support in the market, the X300U-B is the professional-grade choice for a G31 in a duty role.
Glock's own official store lists weapon light options for the G31 platform, confirming factory-endorsed light compatibility paths for owners who want to stay within the official ecosystem.
Glock Rail Compatibility Warning
Do not purchase any light labeled only as "Picatinny compatible" without confirming it explicitly lists Glock rail support.
The Glock proprietary rail has a different cross-slot spacing than the 1913 standard. Lights without the correct Glock-specific key will not seat correctly, shift position under recoil, and create both reliability and safety issues.
Laser Options
Crimson Trace produces Glock-rail-compatible laser and light/laser combination units for large-frame Glock pistols.
The LTG-736 is a rail-mounted green laser/light combination unit confirmed for the G31's Glock-pattern rail. Green lasers are significantly more visible outdoors than red—relevant for a .357 SIG duty pistol that may see outdoor defensive use.
LaserMax produces guide rod laser systems for Glock pistols that install inside the frame without using the rail at all.
The guide rod laser approach preserves rail access for a weapon light, allowing simultaneous rail light and integrated laser use.
Verify the LaserMax unit is listed for the G31 specifically—the guide rod dimensions are barrel-length and generation-dependent.
Magazines for the Glock 31
The G31 uses .357 SIG magazines in a 15-round standard capacity. Glock's magazine ecosystem for the G31 is caliber-specific—do not attempt to use .40 S&W G22 magazines in the G31 without explicit confirmation that the specific magazine feeds .357 SIG reliably.
While the frame dimensions are shared, the cartridge geometry and follower design differ.
Factory Glock Magazines
Factory Glock G31 .357 SIG magazines are the reliability baseline. They are available through Brownells, MidwayUSA, Natchez Shooters Supplies, and the Glock Store.
For any G31 in active carry or defensive use, factory magazines function-tested through at least 200 rounds of your defensive ammunition before trusting them are the correct starting point.
The G31's .357 SIG cartridge operates at higher pressure than .40 S&W and 9mm. Factory magazine spring tension is calibrated for this cartridge—aftermarket magazines using spring weights designed for lower-pressure calibers may cause feeding inconsistencies under sustained use.
Magazine Base Pads and Extensions
NDZ Performance produces magazine base pad extensions for Glock large-frame pistols including the G31.
These replace the factory flush base pad with a slightly extended version that provides a larger gripping surface for faster reload strokes and absorbs impact when magazines are dropped on hard surfaces during competition.
Lone Wolf Arms and Ghost Inc. both produce extended magazine release options and base pad extensions for the G31 platform.
For a duty pistol where reload speed under stress matters, a positive-grip base pad combined with an extended magazine release provides the fastest overall reload sequence without adding bulk that affects concealment.
Capacity Restrictions
The G31's standard 15-round capacity is subject to state magazine capacity laws.
For owners in capacity-restricted states, Glock produces 10-round G31 magazines in factory configuration. Verify your state's current magazine capacity laws before purchasing and carrying standard-capacity magazines.
Triggers and Internal Parts for the Glock 31
The G31's factory trigger is Glock's standard Safe Action mechanism—consistent, reliable, and appropriate for defensive carry use as delivered.
For owners who train at volume and want improved break feel or shorter reset, Glock's mature aftermarket provides several conservative upgrade paths that maintain the Safe Action system's reliability.
Trigger Connectors
Ghost Inc. is the primary documented source for G31 trigger connectors. Their 3.5-pound competition connector reduces the trigger pull weight by changing the connector geometry while maintaining the Safe Action trigger system's function.
Ghost's connectors are drop-in replacements that work with factory Glock trigger components.
For a carry or duty G31, a Ghost connector installed alongside factory springs is the most conservative trigger modification available—it improves break feel without reducing the system's reliability margin.
Do not stack connector modifications with reduced-power spring kits on a duty or carry pistol without extensive reliability testing.
Reduced Power Spring Kits
Wolff and Glock-Trigger.US produce spring kits for Glock large-frame pistols including the G31. A reduced-power striker spring combined with the correct trigger spring reduces perceived pull weight and improves break consistency.
For a carry pistol, verify reliable primer ignition with your specific defensive ammunition after any spring kit installation—.357 SIG uses harder primers in some defensive loads that may require more striker energy than a minimally reduced spring provides.
Extended Controls
Glock's official accessories store lists extended magazine catch, slide stop lever, and front serration slide options for the G31 platform.
NDZ Performance and Lone Wolf Arms also produce extended slide stop levers and magazine releases specifically listed for the G31's generation-appropriate frame.
An extended magazine release provides faster magazine changes under stress. An extended slide stop lever makes it easier to lock the slide back and release it during slide manipulation under stress or with gloved hands.
For a duty or defensive G31, both controls are practical upgrades at minimal cost.
Slide Back Plate
NDZ Performance produces custom back plates for the Glock G31 in multiple designs. These replace the factory black polymer back plate at the rear of the slide with a custom-engraved or colored version.
Functionally identical to the factory plate—a cosmetic customization that also provides identification on a service pistol.
Grip Plug
A grip plug fills the opening at the base of the G31's grip frame, preventing debris accumulation inside the frame when no magazine is inserted.
Glock-pattern grip plugs from multiple vendors fit the large-frame Glock family including the G31. Primarily a maintenance-oriented accessory for a carry pistol exposed to lint, dust, and environmental debris.
Grips and Frame Upgrades for the Glock 31
The G31's factory stippled grip texture is more aggressive on Gen4 and later than on Gen3, but both generations can benefit from additional traction enhancement for wet-condition shooting or sustained range sessions.
Grip Tape and Traction Overlays
Talon Grips produces adhesive grip overlays specifically for the Glock 31 in rubber and granulate textures.
Rubber texture balances traction with daily carry comfort—tacky enough for a secure firing grip without aggressively wearing clothing or skin during concealed carry. Granulate texture is more aggressive and better suited for range use or duty configurations where abrasion against clothing is not a concern.
For a G31 Gen3 with the smoother factory texture, a Talon rubber overlay makes an immediate and meaningful difference in wet-condition grip security. .357 SIG's sharper recoil impulse compared to 9mm makes grip security more consequential per shot.
Magwell
A magwell funnel speeds up reload strokes by creating a larger magazine insertion funnel at the base of the grip. Glock-compatible magwells for the large-frame family from Taran Tactical and Agency Arms provide a more forgiving reload under stress.
For competition use, a magwell is a meaningful speed upgrade. For concealed carry, a magwell adds width and length below the grip frame that increases printing—evaluate the tradeoff against your primary use case.
Optics for the Glock 31
The G31 ships without a factory optic cut. Red dot integration requires either a rear sight dovetail adapter or gunsmith slide milling.
For a legacy duty pistol, the long-term solution is slide milling—it positions the optic at proper height over bore and provides a more secure mounting platform than dovetail adapters.
Slide Milling Options
Zev Technologies, Agency Arms, and independent Glock-experienced gunsmiths provide slide milling services for the G31 in common footprints including RMR, DeltaPoint Pro, and Shield RMSc.
Expect $100–$200 for the milling service depending on footprint choice and gunsmith. The milled cut is permanent—confirm your optic footprint selection before committing.
Dovetail Optic Adapters
Rear sight dovetail adapters from Burris, Shield, and similar makers allow a micro red dot to mount at the G31's rear sight location.
These add height over bore that changes the sight picture geometry and requires taller backup iron sights. For a carry or defensive G31, the simpler and more reliable path is quality tritium iron sights rather than a dovetail adapter.
Practical Recommendation
For most G31 owners, quality tritium night sights remain the better investment than optic integration.
The G31's full-size service pistol role at typical defensive distances does not require a red dot. If you specifically want a red dot on this platform, budget for proper slide milling rather than a dovetail adapter compromise.
Cleaning and Maintenance for the Glock 31
The G31 field-strips identically to other full-size Glocks: drop the magazine, verify clear, lock the slide back, pull the trigger, release the slide lock, and ease the slide forward off the frame.
Routine teardown is straightforward and requires no special tools.
.357 SIG-Specific Cleaning Considerations
The .357 SIG cartridge's higher operating pressure produces more carbon fouling per round than standard 9mm or .40 S&W loads.
The barrel chamber, feed ramp, and forcing cone area accumulate fouling more rapidly under sustained use. Clean the G31's chamber and feed ramp at every cleaning session when running defensive or full-power .357 SIG ammunition.
Copper fouling from jacketed .357 SIG ammunition at higher velocities also accumulates faster than from standard-pressure pistol rounds.
A dedicated copper solvent—Barnes CR-10 or Hoppe's Bench Rest Copper Solvent—addresses copper fouling more effectively than standard carbon bore solvents alone during heavy-use cleaning sessions.
Cleaning Kit Basics
Standard .357 SIG caliber cleaning supplies cover all G31 maintenance needs. A bore brush and patch jag in .357/.38 caliber, cleaning rod, bore solvent, and lubricating oil are sufficient for routine field cleaning.
The Glock Store sells Glock-branded cleaning tools and armorer's kits. Real Avid and Otis produce compact pistol cleaning kits that work with the G31's caliber and barrel length without proprietary tooling.
Glock Armorer's Kit
For G31 owners who perform their own detail strips and internal maintenance, a Glock armorer's tool kit provides the front sight tool (3/16-inch wrench), punch set, and disassembly tools needed for complete internal work.
The Glock Store and Brownells both sell armorer's kit configurations confirmed for full-size Glock platforms.
The front sight tool is particularly important—do not attempt to remove or install the G31's front sight with an improvised wrench.
Lubrication Points
Primary lubrication points on the G31 are the slide rails, barrel hood and feed ramp, and the connector and trigger bar contact surfaces in the frame.
Light oil at these points is sufficient. The .357 SIG's higher operating energy means slide rail lubrication is more consequential than on lower-pressure calibers—dry rails on a high-volume .357 SIG shooting session cause accelerated wear on frame and slide contact surfaces.
Avoid over-lubricating the striker channel. Excess oil in the striker channel attracts carbon fouling from .357 SIG's higher-pressure combustion and can cause light primer strikes in a caliber where reliable ignition is particularly important given the higher-pressure cartridge design.
Cases, Storage, and Transport for the Glock 31
Range and Transport Cases
The G31's full-size dimensions fit standard large-frame pistol cases comfortably.
Pelican 1170 and 1200 hard cases accommodate the G31 with foam cutout inserts and room for spare magazines. Both are lockable and meet TSA requirements for checked baggage.
For range trips, a soft pistol rug prevents slide and frame damage without the setup complexity of a foam-insert hard case.
Quick-Access Safes
For home defense staging, quick-access safes from Hornady, Fort Knox, and Vaultek accommodate the G31's full-size frame. Biometric and push-button models provide fast access in low-light conditions.
Verify internal safe dimensions accommodate the G31 with any mounted light or optic—accessories change the stored dimensions and some compact pistol safes will not fit a full-size Glock with a rail light attached.
Long-Term Storage
Store the G31 with a lightly oiled bore and slide, unloaded, in a low-humidity environment.
Silica gel packs in the storage container control moisture in humid climates. Rotate carry magazines through regular range use to exercise springs—a magazine stored at full compression for extended periods without cycling develops inconsistent spring tension that affects feed reliability.
Gun Belts and Carry Support for the Glock 31
The G31 loaded with a full 15-round .357 SIG magazine approaches 30 ounces. A dedicated gun belt is required for comfortable all-day carry of a full-size service pistol.
Dedicated Carry Belts
A reinforced 1.5-inch gun belt—stiffened leather or nylon with a rigid core—keeps the G31 holster locked in position and distributes the pistol's weight evenly around the waistline.
Standard fashion belts flex under the G31's loaded weight, causing the holster to cant and shift throughout the day. Kore Essentials, Hanks Belts, and Blue Alpha Gear produce quality carry belts in the $60–$120 range.
Nylon Cobra-buckle rigger belts provide excellent rigidity at a lower price point and hold up better than leather in wet or humid conditions.
Magazine Carrier Pairing
A spare G31 magazine carrier must accommodate the large-frame Glock double-stack .357 SIG magazine dimensions.
IWB magazine carriers confirmed for the G31 or Glock large-frame family provide secure retention for concealed carry. For open carry or duty use, a belt-mounted double-retention OWB magazine pouch provides faster access and more positive retention under physical movement.
Best Glock 31 Upgrades
The Glock 31 is a full-size .357 SIG duty pistol with a mature accessory ecosystem built around its large-frame Glock compatibility.
The accessories that deliver the most return are practical and reliability-focused: a generation-confirmed Glock 31 holster, tritium night sights from Trijicon or Ameriglo, a Glock-rail-compatible weapon light with a matched light-bearing holster for home defense, and factory spare magazines function-tested with your carry ammunition.
Internal modifications—a Ghost connector, extended controls, and grip tape—improve the shooting experience without compromising the G31's Safe Action reliability.
The .357 SIG chambering demands slightly more attentive maintenance than standard 9mm, but the caliber's velocity and terminal performance are the reasons the G31 remains a capable and relevant duty and defensive pistol despite its discontinued status.
Generation verification is the recurring requirement throughout every accessory category.
Buy to fit your specific G31 generation, verify Glock rail compatibility before any light purchase, and function-test every modification with your defensive ammunition before carrying the pistol.