OCL Polonium

The Otter Creek Labs Polonium K is a compact, hard-use 5.56 suppressor built from H900 heat-treated 17-4 stainless steel in a CNC welded tubeless design. It is 4.8 inches long, weighs 11.5 oz without a mount, and measures 1.625 inches in outer diameter. The 6mm bore is compatible with 5.56 NATO, .223 Remington, and all 6mm/.243 cartridges including 6 ARC, 6mm Creedmoor, 6mm Dasher, and .243 Winchester. The Polonium K uses industry-standard 1.375x24 HUB rear threads and has a 7.5-inch minimum barrel length requirement for 5.56/.223. Full-auto rated and belt-fed certified with no marketing fluff attached.
 
If you are working through the NFA process for the first time, our complete guide to buying a suppressor online has everything you need.
 
What Makes the Polonium K Different
Otter Creek Labs does not do inflated dB numbers or fancy marketing language. They build suppressors for the working shooter and let the performance make the case. The Polonium K earns its reputation the same way every OCL product does: by being built right, priced honestly, and performing in conditions where lesser suppressors quit.
The H900 heat treatment is not a minor detail. H900 is the highest-strength precipitation hardening condition for 17-4 stainless steel, providing exceptional yield strength and erosion resistance under sustained full-auto fire. Most suppressors use standard 17-4 without this specification. The Polonium K does not cut that corner.
The tubeless design means the baffle structure and outer shell are CNC welded as a unified assembly rather than a separate core inside a tube. The result is higher internal volume for sound reduction, less weight, and no tube-to-core weld joint to fail under hard use. The external geometry is not cosmetic. The material removed from the exterior creates 10% more surface area compared to a conventional design, which means the Polonium K sheds heat and cools faster after sustained strings of fire.
 
The integrated internal and external flash hider is built into the suppressor, not a swappable accessory. On a 5.56K-length suppressor this matters especially in low-light and night vision environments where flash signature reduction is critical. OCL's integrated design outperforms most separate flash hider attachments on competitors.
 
Polonium K vs Polonium: Which One Is Right for You
The Polonium K and the full-length Polonium share the same H900 17-4 stainless construction, same HUB threads, same flash hider design, and same performance philosophy. The difference is size and weight. The Polonium is 5.8 inches and 13.5 oz. The Polonium K is 4.8 inches and 11.5 oz. One inch shorter. Two ounces lighter.
If you run a short-barreled rifle, an MK18-pattern build, or any setup where total package length is a practical consideration, the Polonium K is the right call. If length is not a constraint and you want every bit of available sound suppression, the full Polonium has more internal volume to work with.
 
 
Otter Creek Labs Polonium K Specifications
Otter Creek Labs lets the specs speak for themselves. Here's exactly what you're getting.
Caliber: 5.56 NATO, .223 Remington, 6mm/.243 (6 ARC, 6mm Creedmoor, 6mm Dasher, .243 Winchester)
Length: 4.8 inches
Weight: 11.5 oz (without mount)
Outer diameter: 1.625 inches
Bore diameter: 6mm
Material: H900 heat-treated 17-4 stainless steel
Construction: CNC welded tubeless design
Rear thread: 1.375x24 (HUB standard)
Minimum barrel length: 7.5" for 5.56/.223 and 7.62x39
Full-auto rated: Yes
Belt-fed rated: Yes, on 16" 5.56 belt-fed machine guns. Do not exceed 300-round string without cool down.
Flash hider: Integrated internal and external
Warranty: Lifetime, no BS