Otter Creek Labs Infinity 556K-Base Package-Black

Otter Creek Labs Infinity 556K

The Otter Creek Labs Infinity 556K takes the proven DNA of the full-size Infinity 762 and packs it into a shorter, lighter 5.56 can built for hard-use rifles. It runs across AR-15s, AK hosts, bolt guns, and SBRs without turning your rifle into a brick or causing reliability issues, and the swappable end cap system means you can tune the backpressure instead of living with the factory default.

Features & Benefits

• Additively manufactured Haynes 282 superalloy body built for punishing firing schedules
• Compact 5.5 inch, 14.5 oz footprint that keeps short builds handy
• Rated for 5.56 NATO and 6mm hosts
• Interchangeable back pressure end caps: medium installed, low and high available separately
• HUB 1.375×24 rear thread pattern works with Bravo and most QD mounts on the market
• Lifetime warranty, with an Elite Package that adds all three end caps, a Rearden Atlas mount, and a Rearden SPB brake

Base Package Includes:

• Infinity 556K Suppressor
• One End Cap (Medium, installed)
• Tube Clamp
• Stickers

Elite Package Includes:

• Infinity 556K Suppressor
• High Back Pressure End Cap
• Medium Back Pressure End Cap
• Low Back Pressure End Cap
• Rearden Atlas Mount
• Rearden SPB Muzzle Brake
• Shim Kit
• Tube Clamp
• End Cap Wrench

Infinity 556K Mount Compatibility (HUB / Bravo / 1.375×24)

• Rearden Atlas Moun bundled directly by OCL in the Elite Package alongside the Rearden SPB muzzle brake; the most directly OCL-confirmed pairing available.
• Dead Air Key-Mo and Dead Air Xeno
• SilencerCo Bravo ASR
• Q Plan-B (HUB)
• Griffin Armament A2 Adapter, Plan A, and Dual-Lok
• YHM Kurz QD Adapter and YHM Phantom QD Adapter
• Energetic Armament Vox direct thread mount (such as the OCL ZRO DTA)

Infinity 556K vs Polonium K

Both suppressors come out of Otter Creek Labs, both run the HUB 1.375×24 thread standard, but are built for different jobs.

Infinity 556K: Pick this one when you want to tune gas return to a specific host and ammo combination. The interchangeable end cap system lets you dial backpressure up or down after the sale instead of living with whatever the factory defaulted to.

Polonium K: Pick this one when you want the shortest, lightest 5.56K in the lineup and don’t need to fine-tune backpressure. The fixed tubeless build and integrated flash hider are built for MK18-pattern and belt-fed hard use where size and durability matter more than adjustability.

Shopping the category first? Compare it against our other 5.56 suppressors or explore the full Otter Creek Labs lineup.

Frequently Asked Questions

Which end cap comes installed?
The Infinity 556K ships with the medium back-pressure end cap installed. It’s meant as a balanced starting point that works reasonably well across most hosts before you decide whether you want to swap to the low or high option.

How do I choose low vs. medium vs. high back pressure?
As a general rule, go with the low back-pressure end cap on short-barreled, carbine-length gas systems that already run hot and blow back excess gas toward the shooter, which reduces bolt velocity and felt recoil. Stick with the medium end cap, the factory default, if you’re not sure or you’re running a fairly typical mid-length AR-15. Move to the high back-pressure end cap on hosts that can tolerate more gas dwell bolt guns, piston-driven rifles, or full-size rifle-length gas systems, where the tradeoff buys you a quieter shot instead of extra blowback. Ammo choice affects this too, so treat it as a starting point and adjust based on how your specific host runs.

Infinity 556K or Polonium K, which one for my build?
Go with the Infinity 556K if you want to tune backpressure to your host and ammo over time. Go with the Polonium K if you want the shortest, lightest 5.56K OCL makes and you’re running an MK18-pattern build, a belt-fed host, or anything where total package length and durability matter more than backpressure adjustability. See the full comparison table above for the spec-by-spec breakdown.

What mounts fit the HUB 1.375×24 pattern?
The Infinity 556K’s HUB 1.375×24 thread works with the Rearden Atlas Mount (bundled in the Elite Package), Dead Air Key-Mo and Xeno, SilencerCo Bravo ASR, Q Plan-B, Griffin Armament A2 Adapter/Plan A/Dual-Lok, YHM Kurz and Phantom QD adapters, and Energetic Armament Vox. See the full mount compatibility list above.

Is the FDE finish available separately?
No. FDE Cerakote is only available as part of the Elite Package. If you want the Infinity 556K in FDE, you’ll need to purchase the Elite configuration rather than adding the finish on top of the Base Package.