Otter Creek Arms Llc POLKFDE Polonium K 5.56 FDE

The Otter Creek Labs Polonium K is a compact 5.56 suppressor built for shooters who demand real-world durability and genuine sound reduction without the marketing hype. Engineered as a duty-rated hard-use can, the Polonium K delivers the balance of size, weight, and performance that serious hunters, tactical shooters, and range enthusiasts actually need. At just 4.8 inches long and 11.5 ounces, it won't bloat your rifle or slow you down—yet the design philosophy prioritizes strength and heat management for sustained shooting sessions.

The Polonium K uses a 6mm bore, which means it'll suppress your 5.56 safely while also handling any 6mm or .243 cartridge you throw at it. The standout feature here is the integrated flash hider—both internal and external—that meaningfully reduces muzzle flash when you're shooting in low-light conditions or behind night vision. That's not marketing smoke; it's engineered into the design and reflects Otter Creek's no-nonsense approach to suppressor engineering.

The build itself is H900 heat-treated 17-4 stainless steel in a CNC-welded tubeless design. The exterior gets aggressive material removal in smart places, which does two things: keeps weight minimal and increases surface area for faster cooling. You're looking at roughly 10% more surface area than heavier designs, so thermal cycling during extended shooting won't bog you down. The FDE finish gives you a versatile look that works across modern and traditional rifle platforms.

Mounting is handled via industry-standard 1.375"-24 rear threads, so you can pick the mounting system that suits your needs. The Polonium K ships with a 1/2\"-28 direct-thread adapter, tube clamp for quick changes, stickers, and an instruction pamphlet.

Key Features

• Compact 5.56 suppressor with dual-length options for mounting versatility
• Integrated internal and external flash hider for superior low-light performance and night vision use
• 6mm bore accommodates 5.56, 6mm, and .243 cartridges
• Lightweight design (11.5 oz) without sacrificing strength or durability
• Increased surface area and weight-saving geometry for faster heat dissipation
• H900 heat-treated 17-4 stainless steel construction with CNC-welded tubeless design
• Industry-standard 1.375\"-24 rear mounting threads
• Duty-rated for hard use and extended shooting sessions

Specifications

Frequently Asked Questions

Is the Polonium K compatible with my 5.56 rifle?

Yes. The Polonium K is designed for 5.56 NATO and uses a 6mm bore, so it's safe and effective on any 5.56 platform. It also accepts 6mm and .243 cartridges. The universal 1.375\"-24 rear threads let you choose your mount system—it ships with a 1/2\"-28 direct-thread adapter to get you running right away.

How does the Polonium K perform with night vision?

The integrated internal and external flash hider is designed to provide superior flash reduction, making it well-suited for low-light shooting and night vision applications. The design minimizes visible muzzle signature in those scenarios.

What comes in the box?

You get the suppressor, a 1/2\"-28 direct-thread adapter, a tube clamp for easy mount changes, instruction pamphlet, and stickers.

How does the compact Polonium K compare to the standard length version?

The Polonium K is the short option, measuring 4.8 inches and weighing 11.5 ounces. Both versions share the same build quality, bore size, threading, and flash-hider design—the K sacrifices a little length for easier maneuverability and lighter overall package weight.