The SIG P320's core architecture — a serialized Fire Control Unit that drops into interchangeable grip modules, slides, and calibers — makes it one of the most accessory-friendly handguns available.
That modularity is why the P320 accessory ecosystem is unusually deep: you're not just adding attachments to a static pistol, you're configuring a platform that can serve as a compact EDC, a full-size duty gun, a home defense setup, or a dedicated competition build depending on what you bolt to the FCU.
This guide covers every major SIG P320 accessory category — holsters, optics, weapon lights, grip modules, triggers, slides and barrels, magazines, and maintenance gear — with fitment guidance, variant-specific compatibility notes, and practical context for real-world use.
Holsters for the SIG P320
Holster selection for the P320 requires matching the specific slide length, grip module size, optic footprint, and any rail-mounted light to the holster mold.
A holster cut for a full-size P320 will not fit a Compact slide correctly, and holsters without optic clearance won't seat flush on a pistol with a mounted red dot.
Alien Gear P320 Holsters offers specific rigs across every carry position, with light-bearing and optics-ready configurations for P320 M17, M18, XCarry, XFull, XFive Legion, and XCompact variants with or without lights like the Foxtrot1X, Nightstick TCM-550XL, and Streamlight TLR-7A.
IWB Holsters
IWB holsters work best with P320 Compact and Carry configurations on a 3.9" slide. The P320's striker trigger requires full trigger guard coverage — verify any IWB rig covers the guard completely, especially with an optic installed. Adjustable cant and ride height let you dial in concealment for your body type and carry clothing.
OWB Paddle Holsters
Paddle holsters attach without threading a belt and are practical for range sessions, training, and duty environments where the holster comes on and off frequently. The paddle's wider surface distributes the P320's weight effectively. Confirm rail clearance if you're running a compact WML.
Belt Holsters
OWB belt holsters provide better stability and retention than paddles across extended carry and are the standard choice for duty, open carry, and range work with any slide length. Full-size and M17 configurations carry well in belt-mount OWB rigs.
Appendix Holsters
Appendix carry suits the P320 Compact and Carry sizes. AIWB rigs for the P320 should provide complete trigger guard enclosure and be specifically designed to accommodate compact lights if your setup includes one. Claw or wing attachments help manage the pistol's grip printing under a cover garment.
Hook & Loop Holsters
Hook-and-loop mounting allows quick attachment to plate carriers, vehicle interiors, and non-standard surfaces where belt carry isn't viable. These rigs work across P320 variants and are commonly used in vehicle-mounted defensive configurations and staging roles.
Drop Leg Holsters
Drop-leg rigs mount below the hip, clearing body armor, load-bearing vests, and plate carriers. They suit full-size P320 and M17/M18 builds in tactical and uniformed duty contexts where belt-level access is obstructed by gear. Proper leg strap adjustment prevents holster migration during movement.
Belly Band Holsters
Belly band holsters enable P320 Compact carry without a belt — useful for athletic wear, casual dress, or off-duty situations. Carry position can be adjusted across the torso. These rigs work best with lighter compact configurations rather than full-size builds.
Chest Holsters
Chest rigs keep the P320 accessible during outdoor activities — hiking, hunting, ATV use — where belt carry conflicts with backpack hip belts or seated positions. Padded harness systems distribute the pistol's weight across the shoulders. Full-size and Carry models with rail lights are compatible with chest configurations.
Level 2 Retention Holsters
Level 2 holsters add a secondary retention device — typically a thumb-break hood or locking button — beyond passive friction. These are appropriate for duty carry, vehicle use, and open-carry environments where a retention challenge is a realistic concern. Compatible with full-size, Carry, and M17 configurations.
Level 3 Retention Holsters
Level 3 holsters require defeating three independent retention points before the draw. This tier is standard for uniformed law enforcement and armed security where weapon retention is an active tactical priority. Designed for full-size P320, M17, and M18 configurations in uniform duty roles.
Optics and Sights for the SIG P320
Most current P320 production models ship optics-ready from the factory using SIG's PRO-cut footprint or a plate-based adapter system, eliminating the need for slide milling on recent guns.
The M17 and M18 use a distinct plate pattern from standard P320 slides — buyers must verify plate compatibility before purchasing a red dot for either variant.
Red Dot Compatibility and Plate Systems
SIG's PRO-cut slide accepts plates for the Trijicon RMR, Leupold DeltaPoint Pro, and SIG's ROMEO series, among others. SIG publishes variant-specific compatibility charts, and following them before purchase is non-negotiable — footprints are not universally interchangeable across plate generations or slide families.
For duty and EDC applications, proven drop-test performance, robust housing construction, and reliable battery life matter more than window size or reticle variety.
The Trijicon RMR Type 2 remains the benchmark for durability in harsh environments. Competition shooters running X-Five Legion and P320 MAX builds often prioritize larger windows and multi-reticle options — the Holosun 507C is widely used at this tier for its solar failsafe and competitive price point.
SIG's own ROMEO2 is designed specifically around the P320 footprint and is a natural factory-ecosystem choice.
Suppressor-Height and Iron Sights
Suppressor-height sights are a practical backup for any red dot installation, providing an usable aiming solution if the optic loses power or takes damage. Many X-Series pistols ship with co-witness-ready sights from the factory.
For non-optics builds, SIGLITE night sights from SIG, tritium sets from Trijicon and XS Sights, and fiber optic front sights from several manufacturers all fit standard P320 dovetail dimensions.
Confirm dovetail specifications match your specific slide before purchasing irons. X-Series and AXG slides may differ from standard production in dovetail height or dimensions.
Absolute cowitness aligns dot and irons at the same height; lower-1/3 cowitness places irons in the bottom of the sight picture, which many competition and duty shooters prefer for an unobstructed dot view.
Common Misconceptions
One widespread error: assuming any optics-ready P320 slide accepts any micro dot. Plate systems are generation-specific and variant-specific. Another: running optics without verifying holster clearance.
A holster not designed for your optic footprint will either fail to seat the pistol or place contact pressure on the optic housing, neither of which is acceptable in a carry setup.
Weapon Lights for the SIG P320
The P320's Picatinny dustcover rail is standard on full-size, Carry, and most Compact models, making WML installation straightforward.
The real variable is holster compatibility — light-bearing holsters are mold-specific, and running a light not listed on the holster's supported WML chart can compromise retention or leave the trigger guard area inadequately covered.
Choosing a Compatible Light
Compact builds in the P320 Carry and Compact size benefit from lights like the Streamlight TLR-7A or Nightstick TCM-550XL — both are small enough to avoid significantly widening the pistol's footprint and are explicitly supported by major holster manufacturers.
For full-size duty builds, higher-output lights in the SureFire X300 Ultra or Streamlight TLR-1 HL class match the longer rail and provide substantially more candela for outdoor and longer-range target identification.
Always purchase the holster and light as a compatible pair, not independently. Verify the holster maker lists your specific light model by name before committing to either purchase.
Output, Switchology, and Reliability
Duty-grade WMLs in the 500–1,000+ lumen range provide practical identification capability at defensive distances. More important than peak lumens: consistent activation under stress, reliable tail-cap or paddle switch function in a compressed shooting position, and verified waterproofing for outdoor use.
Streamlight and SureFire have the most comprehensive duty track records and the broadest holster maker support.
Avoid chasing high lumen claims from lesser-known manufacturers at the expense of switch reliability and housing durability. A light that fails in a low-light defensive situation is worse than no light, because it may have driven your holster selection and left you without a compatible standard holster.
Lasers and Combo Units
Light/laser combos from Streamlight and SureFire are available for the P320 rail and provide aiming assistance in non-standard shooting positions — around cover, low-light retention shooting, and force-on-force training.
These units add bulk compared to light-only options and require a holster specifically designed for the combo unit's dimensions. They are more common on home defense and duty builds than on EDC configurations where profile matters.
Grip Modules and Frames for the SIG P320
Because the FCU is the legal firearm, the grip module is an unregulated component that ships directly without a background check. That makes grip changes uniquely accessible on the P320 compared to any platform where the frame is the serialized part.
Factory SIG Grip Modules
SIG produces modules across Full, Carry, and Compact size categories in standard polymer, X-Series, M17/M18 pattern, and AXG aluminum variants. Each configuration changes beavertail geometry, trigger reach, texture aggressiveness, and overall balance.
The AXG series replaces the polymer shell with an aluminum frame — adding meaningful weight and rigidity — and is the foundation of the AXG Legion, a factory-level competition and duty-oriented build.
Module swaps are tool-free on most P320 variants, a process most users can complete in under a minute. This makes it practical to run a Compact module for daily carry and a Full-Size module for home defense or range use while keeping the same FCU.
Aftermarket Grip Modules
Wilson Combat's P320 grip modules are the most consistently recommended aftermarket option.
The improvements are specific and documented: more aggressive grip texture without requiring stippling, a reshaped tang that reduces slide bite with high hand placement, and an undercut trigger guard that allows a higher, more consistent grip.
These changes translate to measurably better recoil control during rapid fire and more consistent draw indexing — particularly relevant for shooters who run the P320 as a duty or EDC gun and log significant round counts.
Other aftermarket modules from Recover Tactical and custom shops address similar ergonomic goals. Regardless of source, verify that the module accommodates your rail-mounted light if you're running one — some aftermarket shells change the dustcover rail geometry or remove it entirely.
Caliber and Size Compatibility
9mm, .40 S&W, and .357 SIG grip modules share external dimensions within each size category. The .45 ACP P320 uses entirely different magazines and grip modules and does not interchange with the three smaller calibers.
Caliber conversions between 9mm, .40, and .357 SIG require a new slide, barrel, recoil spring assembly, and appropriate magazines. The grip module itself does not need to change for those three calibers.
9mm full-size 17-round magazines can often be used in Compact and Carry grip modules with appropriate baseplates or extender sleeves. Running a shorter magazine in a longer grip leaves a gap at the base — functional but cosmetically and ergonomically suboptimal.
Triggers for the SIG P320
The P320's factory trigger is adequate for duty and general use. The platform supports significant refinement, but the key discipline for P320 trigger work is maintaining a clear separation between carry-grade and competition-grade configurations.
Factory Flat Triggers and X-Series Controls
SIG's flat-faced trigger — available through Custom Works and standard on X-Series models — is the most common and safest first trigger upgrade. Flat triggers change the leverage geometry through the pull, which many shooters perceive as a more consistent press and a cleaner reset.
They are factory-supported and maintain SIG's drop safety compliance, making them appropriate for EDC and duty builds without requiring additional reliability testing.
X-Series fire control upgrades and official P320 trigger kits address pull weight, overtravel, and reset distance within factory parameters. These are the appropriate starting point for most users and present no reliability trade-offs when properly installed.
Aftermarket Trigger Kits
Grayguns' P320 Intermediate Duty Action Job is widely used among serious shooters and explicitly preserves drop safety — an important consideration given the P320's history with earlier production drop-safety issues.
It produces a cleaner break and shorter reset without entering unsafe pull weight territory for defensive use.
Apex Tactical and NDZ Performance also offer P320 trigger components: shoes, sear upgrades, and spring kits targeting competition builds. These are appropriate for range and competition guns where pull weight and reset distance are prioritized over defensive reliability margins.
Reduced-weight sear springs and modified trigger bars can produce excellent results in a competition P320 and should stay there — they should not migrate to a carry or duty gun without armorer-level verification and extensive live-fire testing.
What to Avoid
Trigger pull weights below factory spec on a defensive carry gun introduce both reliability risk and legal exposure in a self-defense shooting.
Many firearms trainers and legal experts advise keeping carry gun triggers at or near factory parameters. Any modification affecting drop-safety-relevant FCU components demands chamber checks, slide-drop testing, and extensive live-fire before the gun re-enters a carry role.
Slides, Barrels, and Compensators for the SIG P320
The FCU-driven architecture means slides and barrels are unregulated parts that can be ordered direct.
This enables role-specific configurations — a Carry FCU can become a long-slide competition gun, or a full-size EDC can gain a threaded barrel for suppressor use — without replacing the serialized component.
Aftermarket and Factory Slides
SIG's own optics-ready and PRO-cut slides, including M17/M18-specific kits, are the safest starting point for slide swaps. Third-party slides from Killer Innovations, Faxon, and similar manufacturers offer lightened cuts, aggressive serrations, and pre-milled optic footprints for competition builds.
Tungsten-infused or weighted slides used in X-Five and competition configurations add mass to reduce muzzle flip — these require holsters specifically moded for the added slide profile.
Verify that any aftermarket slide uses a compatible recoil spring assembly and that the barrel lockup is solid before running the combination for defensive use. Slides outside factory specifications can change timing in ways that affect reliability.
Barrels
SIG offers factory threaded barrels for suppressor use across multiple P320 configurations.
Third-party match-grade barrels from Faxon, Lone Wolf, and similar manufacturers target tighter tolerances for competition accuracy. Match barrels generally require a break-in period and may function less reliably with certain ammunition until fully broken in.
Threaded barrels intended for suppressor use require a compatible muzzle device or suppressor with matching thread pitch — 1/2x28 is standard for 9mm P320 barrels.
Confirm your suppressor's thread pitch before purchasing a threaded barrel. Some states restrict suppressor ownership, and short-barreled configurations can create NFA or state-law complications depending on barrel and grip module combinations — know your local laws before building.
Compensators
Micro compensators from Griffin Armament, Agency Arms, and similar companies mount to threaded barrels and reduce muzzle rise on carry and compact P320 builds. The practical benefit is real for high-round-count competition and training use.
For EDC, compensators add muzzle length, require a light-bearing holster replacement or a comp-compatible holster, and complicate the carry profile.
The critical concern with compensators on defensive guns is port-blast at contact distance — gas venting through comp ports in an extreme close-range situation can cause injury and potential reliability issues.
This is a documented limitation that needs to be weighed against the muzzle control benefit for any carry application.
Magazines and Basepads for the SIG P320
SIG OEM magazines are the correct choice for any defensive or duty P320. The 9mm P320 is available in 10-, 15-, 17-, and 21-round capacities depending on configuration and state law. The M17 ships with 17-round mags and is also available with 21-round extended magazines.
OEM vs. Aftermarket Magazines
Experienced users overwhelmingly favor OEM magazines for defensive and duty use and relegate aftermarket magazines to range-only roles.
The P320's modular architecture means the magazine body interacts with the FCU directly — feeding reliability is not a place to accept unknown variables in a defensive gun.
For range and competition use, aftermarket magazines from Magpul (PMAG P320 variants) and other manufacturers have generally performed well, but represent a reliability variable that doesn't exist with OEM mags. Test any aftermarket magazine extensively before relying on it.
Basepads and Extended Magazines
Factory +2 and +3 basepads from SIG increase capacity without requiring a full magazine change and are a practical competition upgrade.
Aftermarket basepads from Springer Precision, NDZ Performance, and Taylor Freelance are widely used in USPSA and IDPA for faster seating, improved grip purchase during reloads, and capacity extension.
The 21-round extended magazine is useful for home defense and competition but adds length below the grip that affects holster selection and concealment on EDC builds. Basepads that increase length require holsters and magazine pouches designed to accommodate the extended floor plate — standard gear may not retain them reliably.
State Capacity Restrictions
Magazine capacity laws vary significantly by state. California, New York, New Jersey, Massachusetts, Colorado, and several other states restrict magazines to 10 rounds for civilian purchase and possession.
Check current state law before purchasing any P320 magazine over 10 rounds — enforcement and compliance requirements vary, and the rules around pre-ban magazines differ state to state.
Maintenance Tools and Cleaning Gear for the SIG P320
The P320's modularity means many users swap components frequently, making proper maintenance tools and disassembly knowledge more important than on non-modular pistols.
FCU-specific bench procedures differ from standard pistol field strip and require attention to pin retention and internal component orientation.
Cleaning Kits and Bore Care
Standard 9mm bore brushes, patches, and solvent work for the P320's barrel. A quality bore snake for 9mm covers field expedient cleaning between range sessions.
For thorough cleaning, the FCU requires separate attention — carbon fouling accumulates in the FCU housing and affects trigger feel and reliability over time if neglected.
Hoppe's No. 9, Slip 2000 EWL, and similar solvents and lubricants are well-suited to the P320's stainless slide rails and FCU components. Follow SIG's lubrication points from the owner's manual — the P320 runs well with minimal lubrication applied correctly, and over-lubrication in the FCU can attract fouling and cause malfunctions.
Recoil Spring Assemblies
The P320's recoil spring assembly is a wear item. SIG recommends replacement intervals based on round count — consult the owner's manual for your specific configuration, as X-Series, full-size, and Compact assemblies differ.
OEM recoil spring assemblies are the correct replacement choice for defensive guns; non-standard assemblies can change cycling timing and affect reliability.
Sight Installation Tools
Swapping sights on the P320 requires a sight pusher compatible with SIG dovetail dimensions. A universal sight pusher with appropriate adapter plates handles this without risking slide or sight damage from improvised methods.
Sight-specific torque drivers for optic mounting screws prevent over-tightening that can strip screws or crack optic housings — Loctite Blue (242) on optic mounting screws is standard practice to prevent loosening under recoil.
Storage and Transport Accessories for the SIG P320
Safe storage and legal transport are part of responsible P320 ownership, and the right gear protects both the pistol and its owner.
Pistol Cases and Range Bags
Hard-sided pistol cases with foam cutouts protect the P320 during transport and are required for airline travel under TSA rules.
Pelican, Plano, and similar manufacturers offer lockable cases that meet airline and range facility requirements. Soft range bags with padded pistol compartments work for vehicle and range transport but do not meet airline hard-case requirements.
For P320 builds with multiple grip modules, slides, and accessories, cases with modular foam allow configuring custom cutouts for each component. This is practical for anyone running the platform in multiple configurations.
Gun Safes and Quick-Access Storage
Quick-access pistol safes — biometric or RFID — keep a P320 home defense build staged and accessible while securing it from unauthorized users, including children.
Hornady Rapid Safe, Fort Knox, and Vaultek make reliable options in this category. A quick-access safe positioned near the bed or in a vehicle console provides faster access than a full-size safe while maintaining meaningful security.
Full-size gun safes from Liberty, American Security, and similar manufacturers secure the P320 alongside the rest of a firearms collection. For P320 builds with significant accessory investment — optics, lights, multiple grip modules — a safe rated for residential security prevents theft loss.
Magazine Storage
Magazine storage racks, pouches, and organized storage containers keep loaded P320 magazines ready without damaging feed lips or springs through improper stacking.
MagLula's UpLULA loader significantly reduces the effort of loading 15- and 17-round P320 magazines — it's a standard bench accessory for high-round-count shooters.
Building Your SIG P320 Configuration by Role
The P320's modular architecture means there's no single correct accessory combination — the right setup depends entirely on how the gun is being used. Mixing carry and competition configurations without discipline creates reliability risks.
Keep these role-based guidelines in mind when selecting SIG P320 accessories.
EDC and Concealed Carry
A P320 Compact or Carry grip module with a 3.9" slide, quality IWB or AIWB holster, OEM 15-round magazines, and a compact weapon light forms a balanced EDC setup. Keep trigger modifications conservative — factory flat trigger at most.
Prioritize concealment, reliable draw from daily clothing, and holster-light compatibility as a matched system. An optics-ready slide with a proven micro dot adds speed without meaningfully changing the carry profile.
Home Defense
A full-size or Carry P320 with a weapon light, high-capacity OEM magazines, and a durable red dot covers home defense requirements. SIGLITE or tritium iron sights serve as backup if the optic fails.
Prioritize white-light output for target identification and train specifically for low-light search and engagement — having the hardware without the skill set is a liability.
Competition
X-Five Legion, P320 MAX, and AXG Legion builds with match barrels, compensators, extended magazines, heavy grip modules, and tuned triggers are the standard competition platform. Keep a strict separation between this configuration and any carry or duty guns.
Competition-tuned triggers, lightened slides, and extended magazine basepads exist only on range guns. Cross-contaminating a competition trigger into a defensive configuration is a documented source of reliability and safety problems.
Duty and Law Enforcement
M17 and M18 configurations with Level 2 or Level 3 retention holsters, OEM magazines, and agency-approved optics are the baseline. Any modifications to duty guns should go through agency armorers and follow department policy.
The P320's FCU modularity gives agencies flexibility in configuration management, but individual modifications outside authorized parameters create liability and reliability concerns that don't exist with factory-spec guns.
Legal and Safety Considerations for P320 Accessories
A few platform-specific points worth knowing before building out a P320 accessory configuration.
The FCU is the serialized, regulated component. Grip modules, slides, and barrels ship as unregulated parts, which makes modular P320 builds legally straightforward in most configurations.
However, certain combinations can create NFA items or state-law violations — a very short barrel length paired with specific grip module configurations can approach SBP territory in states with restrictive laws. Know your state's laws before assembling a non-standard configuration.
Magazine capacity restrictions apply in California, New York, New Jersey, Massachusetts, Colorado, Hawaii, Maryland, and several other states, typically limiting civilian magazines to 10 rounds. Verify current law in your state before purchasing any magazine over that capacity — the rules around grandfathered magazines and transport differ significantly across state lines.
Trigger modifications on defensive guns may receive scrutiny in self-defense legal proceedings. Many experienced trainers and attorneys advise keeping carry gun triggers at or near factory specification. This is not a universal rule, but it is a widely held position worth understanding before making changes to a gun used for self-defense.
Any modification to drop-safety-relevant FCU components — sears, striker components, trigger bars — requires full function testing before the gun returns to a carry role. The P320's drop-safety history with earlier production guns makes this particularly important. When in doubt, consult a qualified SIG armorer.