Sig Sauer P320 Compact
The Sig Sauer P320 Compact is the mid-size member of the P320 modular pistol family — a 3.9-inch barrel, 15-round capacity 9mm that splits the difference between the full-size P320 (4.7-inch barrel) and the subcompact/carry variants. The Compact grip module is the most popular P320 size for shooters who want a pistol that conceals under a cover garment while still providing enough grip length and sight radius for confident shooting at defensive distances.
Read our full P320 Compact Buying Guide ↓
P320 Compact vs. P320 Carry vs. P320 X-Compact
The P320 lineup can be confusing because multiple size designations overlap. The Compact has a 3.9-inch barrel with a compact grip (15-round flush-fit magazine). The Carry has a full-size grip (17-round) with the same 3.9-inch Compact slide — more grip length for shooters who prioritize a full purchase on the gun over concealment. The X-Compact is a further-refined Compact with an X-series flat trigger, enhanced grip texture, and optics-ready slide. If you’re choosing between them: the Compact is the balanced option, the Carry favors grip length, and the X-Compact adds premium features.
Modularity: Swapping Between Sizes
The P320’s defining feature is its serialized fire control unit (FCU) that drops into different grip modules. A P320 Compact FCU can be moved into a full-size, carry, subcompact, or Flux Raider grip module, effectively converting between pistol sizes with a single serialized component. This means buying a P320 Compact is buying into the entire P320 ecosystem — your “gun” is the FCU, and the rest is configuration.
Optics-Ready Variants
Current P320 Compact models ship in both standard and optics-ready (RXP) configurations. The optics-ready slide is milled to accept the Sig Romeo and DeltaPoint Pro footprints directly, with adapter plates available for RMR-footprint optics from Holosun and Trijicon.
P320 Compact as a Duty and Carry Platform
The P320 Compact occupies the same role as the Glock 19 — a mid-size 9mm that works for concealed carry, home defense, and duty use depending on how it’s configured. The P320’s advantage is modularity (one FCU, multiple configurations); the Glock 19’s advantage is simplicity and the largest aftermarket in the industry.
Available Chamberings
The P320 Compact is primarily offered in 9mm. The P320 platform is also available in .40 S&W and .357 SIG in some configurations, with conversion kits available to switch between calibers using the same FCU.
Frequently Asked Questions
What’s the capacity of the P320 Compact?
15+1 in 9mm with the flush-fit compact magazine. Full-size 17-round and extended 21-round magazines also fit.
Is the P320 Compact the same as the M18?
The M18 is the military-contract version based on the P320 Compact/Carry size. The civilian P320 Compact is similar but may differ in specific features and finish.
P320 Compact vs. Glock 19?
Similar size class. The P320 offers modularity and a flat trigger; the Glock 19 offers the largest aftermarket and the widest proven track record. Both are excellent mid-size 9mm pistols.
Can I put a Compact slide on a full-size P320 grip?
Yes — the modular system allows mixing slide and grip module sizes. A Compact slide on a full-size grip is the “Carry” configuration.
See Also: Sig Sauer • Sig P320 • Sig P365 • Flux Raider • 9mm Pistols • Concealed Carry