Sig Sauer P320 Compact 9mm 3.9″ Optic Ready Black
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Specs at a glance
About this product
The Sig Sauer P320 Compact 9mm 3.9″ Optic Ready Black is a striker-fired semi-auto handgun built on a modular fire-control unit that lets you change grip frames and calibers without a trip to the gunsmith. It comes with a factory-milled slide cut for the SIG PRO footprint, SIGLITE night sights, and two 15-round magazines. This is a do-it-all pistol that pulls duty as an everyday carry, home defense, or range gun without any added fluff.
| Manufacturer | Sig Sauer |
|---|---|
| Model | P320 Compact |
| Material | Stainless steel slide, DLC-coated carbon steel barrel, polymer grip module |
| Compatibility | Accepts SIG PRO footprint optics (RMSc, Holosun K, etc.) and standard P320 magazines |
| Finish | Black nitride slide, black polymer grip |
| Weight | 25.5 oz (unloaded, per manufacturer specs) |
| Condition | New |
Key Features
- Optic-Ready Slide (PRO Footprint) — Factory-milled to accept micro red dots without adapter plates. You get a direct mount that keeps the optic low and co-witnesses with the included SIGLITE night sights.
- Modular Fire-Control Unit (FCU) — The serialized chassis is the firearm. Swap grip modules in seconds to change size, texture, or angle without any special tools or FFL transfer.
- SIGLITE Night Sights — Tritium front and rear give you a clear aiming reference in total darkness. They also co-witness with most micro red dots mounted to the PRO cut.
- 15+1 Round Capacity — Compact enough to conceal, but still holds 15 rounds of 9mm. The magazines drop free and have a steel body with a polymer basepad for durability.
Who It’s For
This pistol is for the shooter who wants one platform that can adapt to multiple roles. Whether you’re a new shooter building your first carry gun, a training student looking for a reliable range tool, or a veteran who wants a modular system that fits different hand sizes, the P320 Compact covers you. It’s also a smart choice if you plan to add a red dot later but don’t want to pay for an aftermarket milling job.
Pros / Cons
- Pros: Modular FCU lets you customize grip size and angle. Factory optic cut saves you $100+ in milling costs. SIGLITE sights are bright and durable. 15-round magazines are standard and easy to find.
- Cons: The factory trigger has a bit of take-up and a defined wall; some shooters prefer a lighter, shorter reset after a drop-in trigger kit. The grip module texture is mild — you may want a more aggressive frame for sweaty hands or competition use.
Comparison vs. Competitors
| Feature | Sig Sauer P320 Compact | Zev Technologies OZ9 Compact | Agency Arms Centurion |
|---|---|---|---|
| Price | $487.33 | $1,499+ | $2,500+ |
| Optic Cut | Factory PRO footprint | RMR cut (requires adapter for some optics) | RMR cut (custom) |
| Modularity | Full FCU swap | Chassis-based with steel frame | Fixed frame |
| Weight (unloaded) | 25.5 oz | 28.5 oz | 27 oz |
| Magazine Capacity | 15 rounds | 17 rounds | 15 rounds |
Does the P320 Compact accept the same magazines as the full-size P320?
Yes. The Compact uses 15-round magazines, but it is also compatible with full-size 17- and 21-round P320 magazines. Those longer magazines will extend past the grip, but they function reliably.
Can I mount a red dot without removing the rear sight?
Yes. The factory optic cut leaves the rear dovetail intact. You can install a micro red dot like the Holosun 407K or Sig Romeo X and keep the SIGLITE rear sight for co-witnessing.
What optics fit the PRO footprint on this slide?
The PRO cut accepts optics with the SIG PRO footprint, including the Sig Romeo X, Holosun 407K/507K, and other micro dots using the Shield RMSc pattern. Always check the optic manufacturer’s compatibility list.
Is the grip module interchangeable with other P320 models?
Yes. The P320 Compact uses a “Carry” size grip module (17-round length) or a “Compact” grip module (15-round length). You can swap it with any P320 grip module that matches the FCU size.
Last updated: April 2026
According to NSSF data, the Sig Sauer P320 series accounts for over 15% of the striker-fired handgun market in the U.S., making it one of the most popular modular pistols on the market. This compact model delivers that same reliability in a package that conceals easily and shoots flat.
✔ Nationwide delivery (all 50 states) — ships to your local FFL
✔ Ships 1-2 business days from order
✔ 30-day returns on new, unfired firearms
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Explore more in our Semi Auto Handguns or check out our Optic Ready Pistols and P320 Accessories.