• MR556A4 UPPER KIT 5.56MM 11"
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Heckler and Koch (HK USA)

HK USA MR556A4 Upper Kit 5.56mm 11" – Complete Piston-Driven Upper Assembly

HK USA MR556A4 Upper Kit 5.56mm 11" – Complete Piston-Driven Upper Assembly

$2,220.95
$2,499.00 $2,220.95
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HK51000385

Out of stock

The HK USA MR556A4 Upper Kit delivers a complete 11-inch piston-driven upper receiver assembly chambered in 5.56mm NATO.

  • Type: Complete upper receiver assembly
  • Caliber: 5.56mm NATO
  • Barrel Length: 11 inches
  • Operating System: Gas piston (HK416 system)
  • Barrel: Cold hammer-forged, chrome-lined, 1:7 twist
  • Compatible With: MR556 lower receivers, AR-15 pattern lowers
  • Includes: Upper receiver, bolt carrier group, charging handle, rail system
  • Use: SBR or pistol build (NFA compliance required)
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