HK MR556 A4 SBR 11"

Factory 11" SBR variant of HK's commercial HK416. NFA registration required (no tax under OBBBA).

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Build with This Platform

Key Highlights

•Factory 11" SBR civilian HK416 — same barrel length the SOCOM URG-I and HK416A5 short configurations run
•NFA registration required, but no tax (OBBBA zeroed the SBR stamp)
•Adjustable gas regulator makes it an exceptional suppressor host at short barrel length

Specifications

Price: $3,749
Weight: 7 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 short-barrel configuration of HK's civilian HK416. The 11" barrel matches the length used in the U.S. SOCOM URG-I and HK416A5 carbine — short enough to be genuinely maneuverable inside vehicles and structures, long enough to keep 5.56 terminal performance respectable inside CQB ranges. The adjustable gas regulator and short-stroke piston pair particularly well with a suppressor at this barrel length, where DI guns tend to overgas badly. NFA registration is required (Form 4 transfer or Form 1 if buying the full rifle and registering as SBR), but under OBBBA the federal tax on SBRs has been zeroed and 2026 eForm approvals are running a few days, not months.

Key Features

11" cold hammer-forged barrel, 1:7 twist, 1/2x28 threads
Short-stroke gas piston with adjustable gas regulator
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)
Ships with 30-round STANAG magazine
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
+Civilian HK416 in the SOCOM URG-I barrel length
+Adjustable gas regulator handles suppressor pressure spike 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
−MSRP $3,749 plus FFL/SOT transfer costs
−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