SIG P320 Weapon Light & Laser Fitment Guide

Rail keys, Full Size vs Carry/Compact/XCompact fitment, switch reach, light length, lumens vs candela, batteries, lasers, zero/parallax, holsters, and how to choose a P320-mounted light that actually fits the gun and the job.

M1913 Rail   |   Rail Keys   |   Lumens   |   Candela   |   Switches   |   Batteries   |   Lasers   |   Holster Fitment

The P320 is easy to hang a light on. Picking the right light is where things get more interesting.

Most current P320 grip modules use an M1913/Picatinny accessory rail, but that does not make every pistol light a perfect drop-on fit. The cross-slot key, rail position, trigger-guard clearance, switch reach, light length, grip-module rail length and holster all matter. SIG's own FOXTROT2R fit list covers P320 Compact, XCompact, XCarry, XFive, Full Size, Carry, M17 and M18 — but specifically excludes the older Subcompact and LIMA grip modules. [S1-S3]

Then comes the beam itself. A compact 1,100-lumen light can produce a very different beam from a 650-lumen light with 66,000 candela. One floods a room better; the other punches farther downrange. Output, intensity, runtime, battery system and size are all separate variables. [S4-S7]

So this guide starts with fitment first, then performance. Because a monster spec sheet is useless if the switch is in the wrong place, the rail key is wrong, or your holster will not take the gun anymore.

“The best P320 light is not the one with the biggest number. It is the one that fits the rail, reaches your fingers, fits the holster, and puts the right beam where you need it.”

Current SIG X-Series P320 grip modules list an M1913 Picatinny accessory rail. [S3] That tells you the basic interface, but a pistol light still needs to index correctly into one of the cross slots and sit at the right fore/aft position.

Streamlight's TLR-1 HL makes this unusually obvious: it ships with separate rail keys for Glock-style rails, MIL-STD-1913 rails and a dedicated SIG SAUER P320 key, among others. [S4]

On the TLR-7/TLR-8 family, Streamlight's current instructions say to choose a rail key that matches the slot width, switch position and trigger-guard clearance. The manual states flat-out that a key must be used or the TLR can slide off the rail under recoil. [S8]

So if a light clamps onto the rail but the key does not positively engage a slot, that is not “close enough.” Fix the key/insert choice before live fire.

SIG's current FOXTROT2R is a useful fitment reference because SIG publishes the compatible P320 families directly: Compact, XCompact, XCarry, XFive, Full Size, Carry, M17 and M18. SIG excludes the old P320 Subcompact and LIMA grip modules. [S1-S2]

The light uses an M1913 attachment, ships with two rail-interface inserts, and gives the user four sliding insert positions to tune switch location. It is rated at 700 lumens and 20,000 candela and can run either an included 16340 rechargeable cell or a CR123A. [S1]

The useful lesson is not “buy SIG because SIG.” It is that fore/aft adjustability and the correct interface insert matter on a modular pistol with several frame lengths and different hand sizes.

There is no mechanical rule saying a compact P320 must wear a compact light or a Full Size must wear a full-size light. The decision is mostly about rail fit, switch reach, beam requirements, overall package length and holster support.

These are examples, not a ranking. Their specs show why you cannot choose a weapon light from lumens alone.

That X300T row is the easiest way to kill the “more lumens = farther reach” myth. It has fewer lumens than every other example in the table and the highest candela by a mile. [S6]

Lumens describe total visible light output. Candela describes directional intensity. Neither number by itself tells you the whole beam.

For indoor/general-purpose use, broad spill can be extremely useful because it lights a large nearby area. For outdoor identification, long hallways, large properties or working through strong competing light, more candela can preserve a brighter central hotspot at distance.

Do not buy the number. Buy the beam pattern that matches where the pistol is expected to work.

A light can be mechanically secure and ergonomically wrong.

Short fingers, long fingers, large grip modules, different trigger-guard shapes and high/low paddle options all change whether you can operate the light without destroying your firing grip. Streamlight's TLR-7 family includes interchangeable high/low paddles specifically to accommodate different shooting styles. [S5][S8]

SIG takes another approach with FOXTROT2R: its four-position sliding rail insert lets the whole light move to put the activation paddles where the user wants them. [S1]

If you have to break your grip or reach into the trigger guard to operate the light, the mounting position is wrong for you.

Modern pistol lights increasingly use dual-fuel systems. That is useful, but the battery choice can change output.

The current TLR-7 HL-X, for example, produces its highest advertised output with Streamlight's rechargeable SL-B9 battery and lower output with a CR123A. [S5] FOXTROT2R is specified for either a rechargeable 16340 or CR123A while maintaining its published 700-lumen / 20,000-candela specification. [S1]

The practical choice depends on use:

• Rechargeable: cheap to train with, easy to top off, often enables maximum output.
• Primary lithium: long storage life and easy spare-battery logistics.
• Dual fuel: gives you both options, but learn what each battery actually does to output and runtime.

Once a weapon light is mounted, holster fit is no longer just “P320 Full Size” or “P320 Carry.” It is P320 + exact light + slide length + optic + other external accessories.

SIG's own BlackPoint P320 light-bearing holsters make the point clearly: models built around FOXTROT lights specifically say other light brands/models are not compatible and warn against substituting a different light. [S9]

If the pistol is intended for carry, duty or serious use, pick the light and holster as a pair instead of buying one and hoping the other happens to fit.

Not automatically. A full-size X300/TLR-1-class light sticking past a 3.9-inch Carry slide is a normal configuration and has a huge holster ecosystem.

The tradeoffs are package length, weight, concealment and more carbon on the lens/bezel because the light sits closer to or beyond the muzzle. The benefit is that a longer light can provide a larger optical system, more battery capacity and a larger support ecosystem.

On the other side, a compact light can keep the front of a Carry/XCompact build much shorter. Neither configuration is “correct” in isolation.

A visible laser gives you an aiming reference projected onto the target. It does not identify what the target is. A white light and a laser solve different problems.

The current Streamlight TLR-8 X combines a 500-lumen / 5,000-candela light with a user-adjustable red laser on a compact rail-mounted package. [S10] SIG's LIMA320 took a completely different approach by integrating the laser into a Compact-size P320 grip module. SIG lists it for Compact, Carry and Full Size 9mm/.40/.357 P320s while excluding .45 ACP and manual-safety variants. [S11-S12]

That LIMA example is a good reminder that “laser fitment” can mean the entire grip module rather than the accessory rail.

A rail-mounted laser sits below the bore. That physical offset never disappears. When you zero the laser to intersect the bullet path at one distance, the two lines cross at that distance and separate again beyond it.

Streamlight's TLR-8 instructions explicitly discuss this geometry. The manual notes that a handgun laser can be adjusted so bullet strike stays roughly within a useful vertical band over typical handgun distances, but the exact relationship depends on the chosen zero and emitter location. [S13]

Crimson Trace uses 50 feet as its factory laser zero starting point and likewise calls out parallax from the physical offset between the laser and bore. [S14]

Do not “zero” a laser by making it overlap the iron sights across the room and assume the job is finished. Pick a distance, understand the offset, then confirm with live fire.

A rail clamp squeezes the light onto the rail. The cross-slot key prevents fore/aft movement under recoil. You want both.

Streamlight's current mounting instructions tell the user to align the key with the correct rail groove, snap the clamp into place and tighten the tension bolt only until securely attached. [S8]

If the light walks forward, shifts under recoil or changes switch position, do not immediately crank the clamp tighter. Verify the correct key and slot first.

A weapon light is not “installed forever.” Check it like another piece of mounted equipment.

• Verify the clamp and key are still secure.
• Test momentary and constant-on controls.
• Keep the lens clear enough that carbon is not destroying useful output.
• Replace or recharge batteries on a schedule instead of waiting for the light to look obviously weak.
• After changing batteries or removing the light, verify that it returned to the intended rail slot and switch position.

IronKells P320 Buying Paths

Bottom Line

The P320 gives you a lot of rail space and a lot of lighting options. Use that flexibility instead of treating it like a universal mounting surface where every light is automatically equivalent.

Verify the rail and key. Put the switch where your hands can actually reach it. Pick the beam for the distances you care about. Decide whether battery logistics matter more than headline output. Then make sure the holster is built around the exact light.

Fit first. Beam second. Holster third. Then prove the whole package together.

Pick the Beam for the Job — Then Make the Whole Pistol Fit Around It

Rail key, switch position, light body, holster and battery system are all part of the weapon-light setup.

Product specifications and fit lists change. These sources were reviewed October 2, 2026. Verify the current manufacturer fit guide and your exact P320 grip module before purchase.

A Rail Gives You Options. Fitment Decides Which Ones Actually Work.

Mount it correctly. Reach the switches naturally. Pick the right beam. Fit the holster around the exact light. Then go prove it.