SIG SAUER P320 MOD 9MM COMP ROMX 4″ 21+1

Description

If you’re looking for a factory-compensated, ready-to-run defensive pistol that handles flat and shoots fast, the SIG SAUER P320 MOD 9MM COMP ROMX 4″ 21+1 is a genuine workhorse. This model pairs SIG’s proven modular chassis with an integrated compensator and the crisp ROMX optic, giving you competition-ready accuracy right out of the box. At $1329.99, it’s a solid investment for shooters who demand reliability without extra gunsmithing.

Manufacturer	SIG SAUER
Model	P320 MOD 9MM COMP ROMX 4″ 21+1
Material	Stainless steel slide with polymer grip module (per manufacturer specs)
Compatibility	P320 holsters and magazines (standard and X-Series)
Finish	Nitron® black finish on slide, black polymer grip
Weight	29.5 oz (unloaded, with optic)
Condition	New

Key Features

• Integrated Compensator — Reduces muzzle rise and felt recoil by roughly 30% compared to a standard P320 barrel, letting you stay on target for fast follow-up shots. Why it matters: less flip means tighter groups and quicker splits, whether you’re shooting steel or defending your home.
• ROMX Optic Ready — Factory-mounted ROMX red dot with a 3 MOA dot and a rugged aluminum housing. Why it matters: you get a premium optic zeroed from the factory, saving you time and the hassle of aftermarket milling.
• 21+1 Round Capacity — Full-size grip holds two extra rounds over the standard 17-round magazine. Why it matters: more ammunition on tap without extending the grip length, ideal for IDPA and range sessions.
• Modular Grip System — Swap grip modules in seconds to fit different hand sizes or concealment needs. Why it matters: one gun fits multiple shooters or carry styles, reducing the need for separate firearms.
• Flat Trigger — SIG’s X-Series flat trigger with a clean 4.5 lb break and short reset. Why it matters: consistent trigger pull improves accuracy and speed, especially under stress.

Who It’s For

This pistol is built for the southern shooter who wants a flat-shooting, optic-ready handgun for competition, home defense, or range days. If you’re a dove hunter who appreciates a fast second shot on a covey rise, you’ll love how this gun keeps the dot on target. It’s also a great choice for the growing number of shooters who prefer a factory-compensated pistol without the hassle of aftermarket parts.

Pros & Cons

• Pro: Factory-compensated design reduces muzzle flip significantly, making it easier to shoot accurately under time pressure.
• Pro: ROMX optic is rugged and holds zero well, with a clear dot for fast acquisition.
• Pro: 21+1 capacity gives you a competitive edge in USPSA and IDPA matches.
• Con: The compensator adds about 0.5″ to the overall length, which may affect holster fitment with some standard P320 holsters. Per SIG SAUER specs, you’ll need a holster designed for a compensated slide or a full-size P320.

Comparison

Feature	SIG P320 MOD COMP	Zev Technologies OZ9	Agency Arms AOS
Caliber	9mm	9mm	9mm
Barrel Length	4.0″ (with comp)	4.5″	4.6″
Optic	ROMX (included)	None (optic cut)	None (AOS cut)
Capacity	21+1	17+1 (standard)	17+1 (standard)
Compensator	Integrated	Optional (aftermarket)	Optional (aftermarket)
Price	$1329.99	$1,699+	$1,899+
Best For	Value + factory comp + optic	Custom builders	Duty/competition shooters

Frequently Asked Questions

Does the compensator make the P320 MOD louder or affect reliability?

Yes, the compensator can increase perceived noise slightly, but it’s within normal range for a 9mm pistol. Reliability is excellent with factory 115-grain and 124-grain ammo. Per SIG SAUER specs, the gun is tested with standard pressure loads and functions without issue.

Will this fit my existing P320 holster?

It depends on the holster design. The compensator adds about half an inch to the slide length, so holsters molded for a standard 4.7″ P320 slide may not fully cover the muzzle. Look for holsters specifically for the P320 MOD or full-size compensated models.

Can I swap the ROMX optic for another brand?

Yes, the ROMX uses a standard Shield footprint, so you can mount optics like the Holosun 407K/507K or SIG ROMEO Zero with an adapter plate. The factory ROMX is a solid choice for most shooters.

Is the 21+1 magazine compatible with other P320 models?

Yes, the 21-round magazine works with any full-size P320 grip module. It will also fit X-Series grips, though it may protrude slightly if you use a compact grip.

Why Buy From Us

• ✓ Nationwide delivery (all 50 states)
• ✓ Ships 1-2 business days
• ✓ 30-day returns
• ✓ Secure checkout

Browse more Semi Auto Handguns or check our SIG SAUER Pistols for similar models. Also see Optics & Red Dots for upgrade options.

Last updated: April 2026