Irregular Design GroupHesychia 556UK-HUB
5.56mm / .223 suppressor · HUB 1.375x24 interface · specs and compatibility from the manufacturer
Notable features
- HUB Compatible
- Low Backpressure
- Full-Auto Rated
- Sealed
length
4.18″
weight
11oz
MSRP
$825
length
4.18″
weight
11oz
calibers
5.56
material
Inconel
interface
HUB 1.375x24
MSRP
$825
- Overall length
- 4.18″
- Class
- 5.56mm / .223
- n
- 328
- Range
- 2.5″–9.75″
- Median
- 6.12″
- Diameter
- 1.75″
- Class
- 5.56mm / .223
- n
- 328
- Range
- 0.98″–2.2″
- Median
- 1.57″
- Weight
- 11 oz
- Material
- Inconel 718
- Max caliber
- 5.56mm NATO
- Base interface
- HUB 1.375x24
- Front cap
- Fixed
- Backpressure
- Low
- Full-auto rated
- Yes
- Barrel restriction
- 10.3" minimum
- Maintenance
- Sealed (not user serviceable)
- MSRP
- $825
Shorter than most 5.56mm / .223 suppressors
Length compared against the 328 5.56mm / .223 suppressors in the catalog that publish one. Quartile basis; a value inside the middle half carries no note.
Wider than most 5.56mm / .223 suppressors
Diameter compared against the 328 5.56mm / .223 suppressors in the catalog that publish one. Quartile basis; a value inside the middle half carries no note.
Prices are manufacturer's suggested retail (MSRP). What you pay may differ.
- Base interface
- HUB 1.375x24
- Front cap
- Fixed
The HUB 1.375x24 is an open standard: 415 mounts and 818 muzzle devices in our catalog fit this suppressor, including Irregular Design Group Hesion Bow HUB Adapter, AAC 51T S.T.A.M.P. Mount and AB Suppressor AB Raptor Adapter. You aren't locked into one manufacturer's parts.
Which ones fit your barrel and host?
Check in the BuilderManufacturer claim
- The 556UK-H is full auto rated, with a low backpressure gas profile.
- Irregular Design Group measures the 556UK-H at 136 dB at the ear and 140 dB at the muzzle on a DD MK18 10.3 test platform, both muzzle-device dependent.
- The 556UK-H was designed for shooters who want the 556UK's gas and flash behavior in a HUB format. If you need maximum abuse margin in this family, the Hesychia SIXK is the better option.
- Irregular Design Group designed the system so it does not need any tuning for any firearm host it mounts to — no adjustable gas blocks, heavier buffers, or different springs required to make the suppressor work.
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- The 556UK-H is the HUB version of the Hesychia 556UK, keeping the same core design logic in a 1.375-24 TPI HUB interface instead of the native Hesion Bow lock.
- 4.18" overall length and 11 oz, with 2.8" between the blast baffle and the front face and a 1.34" chamber depth.
- The 556UK-H biases toward a higher compartmentalized pressure zone and uses a deep recessed exit aperture region so the six exit ports pull gas from the central core where mixing is at its highest, rather than venting directly out of the bore line.
- The 556UK-H is a monolithic Inconel 718 body produced by Laser Powder Bed Fusion (LPBF), with the critical interfaces machined afterward.
- Inconel 718 is the material choice because it holds its shape, resists erosion, and survives thermal cycling. It is not the lightest option and not the cheapest option.
- The 556UK-H is a sealed monolithic unit. There are no user-serviceable internal components and no baffles to remove individually.
- The 556UK-H works with both the Hybrid Flash Hider and the Micro Flow Enhancer, but because both are Hesion Bow muzzle devices, running either one requires the Hesion Bow HUB Adapter.
- There is no Macro Flow Enhancer path for the 556UK-H: the Macro FE is too long to work within the 556UK geometry when using the Hesion Bow HUB Adapter.
- The 556UK-H is full auto rated for 10.3" barrels and above. The minimum recommended barrel length for the 5.56 and 6mm rifle suppressors in this system is 10.3", and going shorter increases blast baffle erosion and raises projectile stability risk.