SIG MPX 9mm 4.5" PCB Brace M-LOK, 35-Round Capacity

The SIG MPX 9mm PCB brace platform is a gas piston–driven compact carbine built on the same reliability principles that made the full-size MPX a favorite with professionals and serious shooters. With a 4.5-inch barrel and the factory folding PCB brace, this 9mm fires from a closed-bolt system engineered for consistency and durability in a size that stays under 6 pounds—ideal for home defense, vehicle stashing, or anyone who wants modern ergonomics and real carbine performance in a short package. The modular design means you can tailor it to your mission: swap handguards for different sight lines and suppressor wrap, add optics to the picatinny top, and run the included 35-round magazine or go lighter if you choose.

The heart of this gun is the Timney single-stage trigger, co-engineered with SIG to deliver the crisp, predictable break Timney shooters expect without sacrificing the sub-gun durability. Cold hammer-forged 9mm barrel, hard-coat anodized receiver, and a full-length M-LOK handguard give you a modern, maintainable platform that handles suppressors out of the box. The PCB brace folds tight—the gun compresses to less than 23 inches, making it legitimately easy to store or move, and you can still fire it with the brace deployed or folded, giving you options when space or stance matter.

This is a shooter's platform, not a range toy. If you run suppressed 9mm, want a short-barrel carbine that doesn't require exotic ammunition, or need a compact, serious gun that plays well with modern accessories, the SIG MPX 9mm with PCB brace and M-LOK is a no-compromise choice. Comes with one 35-round magazine and ready to go.

Key Features

• Closed-bolt gas piston operating system for reliable, smooth cycling
• SIG PCB folding brace—folds to ultra-compact size, operable folded or deployed
• Timney single-stage trigger co-designed with SIG for precision and durability
• Cold hammer-forged 9mm barrel with M13.5 x 1 mm suppressor threads
• Full-length M-LOK handguard for modern accessory mounting and suppressor coverage
• Hard-coat anodized receiver and polymer grip for light weight and corrosion resistance
• Includes one 35-round MPX polymer magazine
• Modular design—barrel lengths and handguard options available separately

Specifications

Frequently Asked Questions

Can I use this with a suppressor?

Yes. The 4.5-inch barrel comes threaded M13.5 x 1 mm for suppressor use. The full-length M-LOK handguard is designed with suppressor coverage in mind, and you can mount optics independently on the picatinny rail.

What is the PCB brace and how does it fold?

The PCB (Pictinny Controlled Brace) is SIG's folding brace. It allows the gun to collapse to a more compact size for storage or transport and remains functional—you can fire the gun with the brace deployed or folded, depending on your grip and stance preference.

Is the handguard modular?

Yes. The current gun ships with a full-length M-LOK handguard, but the MPX platform is modular. Different handguard lengths and barrel lengths are available separately as upgrades or customization options.

What trigger does this come with?

The SIG MPX 9mm features a Timney single-stage trigger. It's co-engineered by Timney and SIG to deliver consistent break and reliable performance in a subgun platform without sacrificing durability.