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Heckler & Koch

HK MR556 A4 SBR 11"

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

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
$3,999
Weight
6 lb 11 oz
Calibers
5.56x45mm
Rail Type
mlok

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
  • No published HK SBR MSRP; public 11" pistol MSRP is $3,999
  • 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

Detailed Specifications

caliber
5.56 NATO
Barrel Length
11"
Overall Length
27.9" - 31.7"
weight
6.7 lbs
Gas System
Short-stroke gas piston with 2-position adjustable gas block
railSystem
Slimline M-LOK handguard with 16.75" Picatinny top rail
Trigger
Two-stage, 4.5-5.6 lb approximate
Twist Rate
1:7 right-hand, 6 lands & grooves
threadPitch
1/2x28
msrp
No published SBR MSRP; public 11" pistol MSRP $3,999

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+705 more

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