P320 vs. P365: What's The Difference?

Sig Sauer now has two wildly popular handguns on the market. Both are modular, and both effectively function in the same manner. We're talking about the P320 and P365. Given that both pistols use an internal chassis with reconfigurable frames, slides, and barrels, it's easy to get confused when it comes to the differences between these two pistols. Let's clear it up.

P320 vs. P365: Key Differences

Here's the short n' sweet of these two pistols: The P365 is a smaller version of the Sig P320. The P365 is, in its base form, considered a micro- or sub-compact that's designed for concealed carry, while the P320 can be configured as a full-sized duty pistol, or a more compact pistol that, generally, will still be larger than the P365.

Pictured left, the standard P365 is significantly smaller than the standard P320. The P365 is 5.8" long and 4.3" tall, while the P320 is 8" long and 5.5" tall. The P365 measures 1.06" to 1.1" wide, while the P320 measures 1.3" to 1.4" wide (we cover the guns' other dimensions below).

The P365 is chambered in 9mm or .380, while the P320 is chambered in 9mm, .357 SIG, .40 S&W, 10mm Auto, and .45 ACP.

P365 vs. P320 Fire Control Units

Sig Sauer developed both guns with an internal, modular fire control unit (FCU), allowing either gun's barrel, slide, and frame (called an exoskeleton by Sig) to be swapped out. This allows both guns's dimensions and calibers to be easily reconfigured. Although the P365's (left) and P320's (right) FCUs function virtually identically, they and their parts are not interchangeable; the P320's FCU is wider, taller, and longer than the P365's.

P320 vs. P365 Size Differences

Both guns' FCUs allow either pistol to be significantly resized. In the P365's case, it can be made even larger than some P320 models, and the P320 can be made into a properly small compact. Below are the available configurations for both pistols, with basic dimensions listed for their components.

Available P365 Configurations

The P365 is, by default, configured with a "standard" frame (called a Grip Mod by Sig). This is the smallest available frame. The other available options, increasing in size, include the P365XL, P365XL LXG -- which increase the magazine well length for a higher magazine capacity -- and, finally, the "Macro" frame, which increases magazine well length even further and increases the forward length of the frame to incorporate an under-slide Picatinny rail.

No matter what frame size you select, you'll be limited to two slide lengths: 3.1" and 3.7". No matter which frame you select, you'll be able to install either slide length on your P365.

The P365 offers two barrel lengths: 3.1" and 3.7". The barrel does not have to match the slide length. You can, for example, install a 3.1" barrel on the P365 and install a 3.7" slide with ports that will direct the muzzle blast upward to reduce muzzle flip.

Lastly, the P365 offers three factory magazine capacities: 10, 12, and 17 rounds, the last of which are extended mags. The smallest magazines (10-rounds) fit both all frames. To fit the larger frames, the 10-round magazines incorporate a fixed extension piece that does not increase its ammo capacity, which may be required in some restrictive states.

To recap, the P365 offers the following options:

• Four Frames: Standard, XL, XL LXG, and Macro
• Two Slides: 3.1" and 3.7"
• Two Barrels: 3.1" and 3.7"
• Three Magazines: 10, 12, and 17 rounds

You can play around with the P365's various available configurations using Sig's "Custom Works" P365 Studio.

Available P320 Configurations

The P320 has even more component options available to customize the gun's size and caliber. Its frames are categorized into three sizes: Full, Carry, and Compact. Across these three sizes, the P320 offers more than 40 frames (also called grip modules) in various colors, with and without Picatinny rails.

The P320 offers four slide lengths: 3.6", 3.9", 4.7" and 5". Not that, unlike the P365, the P320's slides aren't universally compatible with all its available grip modules. For example, a 3.6" slide won't fit on a Full-Size grip module.

Like the P365, the P320's barrel lengths correspond with its slide lengths -- but there are also barrel lengths available that fall in between each slide length. Available barrel lengths include: 3.6", 3.9", 4.3", 4.6", and 5.5".

The P320 has more magazine options, with far higher magazine capacities to boot. They include: 10, 15, 17, and 21 rounds. But unlike the P365, the P320's magazines aren't universally compatible with all grip module sizes. For example, its 10-round magazine options won't fit in its Full-Size or Carry grip modules.

To recap, the P320 offers the following options:

• Three Frames: Full-Size, Carry, and Compact
• Four Slides: 3.6", 3.9", 4.7" and 5"
• Five Barrels: 3.6", 3.9", 4.3", 4.6" and 5.5"
• Four Magazines: 10, 15, 17, and 21 rounds

You can test various P320 configurations by using Sig's "Custom Works" P320 Studio.

P320 & P365: Swapping Calibers

It's here that both guns function identically. In addition to being able to swap individual components -- like all those mentioned above -- you can easily strip your P320 or P365 FCU down to the bare unit, and convert your pistol's caliber and configuration in one go using something called an "X-Change" kit. The X-Change kits include a grip module, slide, barrel, operating rod and recoil spring, and magazine.

One of the P365's kits allows you to convert your pistol from 9mm to .380 (exampled here, and pictured above), while the P320's kit allows you to convert your pistol to chamber 9mm (available here). Other X-Change Kits exist that provide different calibers and pistol sizes.