The Sig P320 in .40 S&W is a discontinued variant — Sig has shifted the P320 line almost entirely to 9mm, and the .40 version is now secondary-market inventory from dealers who stocked it before production ended. That matters for buyers: parts availability and support are tied to the 9mm P320 ecosystem, which remains active, but finding a new .40 P320 takes searching. Specs are solid for what you get: 14+1 capacity, 4.7" barrel, 29.5 oz, and the P320's modular fire control unit (FCU).

The FCU is the serialized part in the P320 — the grip module is just a polymer shell. That means a single P320 FCU can be moved between full-size, compact, and X-series grip modules without a new firearm transfer. In practice, a buyer who purchases this .40 full-size P320 can later swap to a compact grip module (if they can find .40 compact modules) for carry use. The 6.5 lb trigger pull matches the S&W M&P 40 exactly; the HK VP40 runs notably lighter at 5.4 lbs. Reviewers generally place the P320's striker trigger between the Glock G22's 5.9 lb pull and the M&P 40's 6.5 lb break in terms of feel, though the spec here is 6.5 lb for this variant.

The real surprise with the P320 is both its biggest strength and its most documented problem. The modularity — FCU swappable between grip sizes without a new serial number — is genuinely unusual in the service pistol market. No other major duty pistol works this way. The documented weakness is the drop-fire history: pre-2017 P320s had a known issue where the pistol could discharge if dropped at certain angles. Sig ran a Voluntary Upgrade Program (VUP) that revised the trigger group and sear geometry. Current production P320s have the VUP design. Any pre-VUP gun should be submitted for the upgrade before use.