HK MR556 A4 SBR 11"

Factory 11" LE SBR variant of HK's MR A4 line; NFA registration required.

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Key Highlights

•Factory 11" MR A4 LE SBR configuration
•NFA registration required; federal SBR making/transfer tax is currently $0
•Adjustable gas regulator makes it an exceptional suppressor host at short barrel length

Specifications

Price: $4,299
Weight: 6 lb 11 oz
Calibers: 5.56x45mm
Rail Type: mlok
Best For: vehicle ops home defense duty patrol

Capability Profile

0-10 Scale Across 8 Axes

Compatibility Tags

family: modern-riflefamily: ar-patterntrigger: ar-fcginterface: picatinny-tophandguard: mlokbarrel: compactthread: 1/2x28mag-type: stanag

Overview

The MR556 A4 SBR is the factory 11-inch LE short-barrel configuration in HK's MR A4 family. The 11-inch barrel is short enough to be genuinely maneuverable inside vehicles and structures while keeping the MR A4 short-stroke piston operating system and ambidextrous controls. The 2-position adjustable gas block pairs well with a suppressor at this barrel length, where direct-impingement guns often need extra tuning. NFA registration is still required; the federal SBR making/transfer tax is currently $0.

Key Features

11" cold hammer-forged barrel, 1:7 twist, 1/2x28 threads
Short-stroke gas piston with 2-position adjustable gas block
Fully ambidextrous controls
HK Free Floating M-LOK Rail System
Optic-ready full-length Picatinny top rail
Tungsten-filled proprietary buffer (designed for short-barrel gas curve)
Available in 10- or 30-round configurations depending on SKU and jurisdiction
Same MR556 A4 lower as the 16.5" rifle (parts compatibility)

Pros

+Factory-built SBR — no Form 1 build, no pinned-and-welded muzzle device
+Factory 11" MR A4 SBR configuration
+2-position adjustable gas block handles suppressor pressure changes cleanly
+Short-stroke piston keeps the action cooler than DI in 11" configurations
+Same proven HK QC as the 16.5" rifle

Cons

−NFA item — requires Form 4 transfer and registration paperwork
−$4,299 MSRP is one of the priciest factory 5.56 SBRs available
−11" barrel sacrifices muzzle velocity (~2,650 fps with M193 vs ~3,100 fps from 16")
−Proprietary barrel and gas system limit aftermarket length swaps