Heckler & Koch MR556A4 Upper Kit 5.56mm 11" HK51000385

H&K USA: HK51000385—mr556a4 upper kit 5.56mm 11". MR556 Upper 11" (No UPC).

HK51000385: H&K MR556A4 11" Upper Receiver Kit

HK51000385: Complete Heckler & Koch MR556A4 upper assembly with 11" cold hammer forged barrel, piston system, free-float rail. 5.56 NATO, mil-spec quality for SBR builds or uppers.

Key Features and Specifications

• Caliber: 5.56x45mm NATO
• Barrel: 11" CHF Triangular
• System: Short-Stroke Piston
• Rail: Quad Free-Float
• Model: HK51000385

Heckler Koch HK MR556A4 Upper Receiver Kit 11 Inch Barrel 5.56 Piston Driven Cold Hammer Forged Short Stroke Gas Free Float Rail SBR Build AR15 Compatible Precision

HK mr556 upper; 11. "Piston power!" Upper hk.

Pros and Cons

Pros:

• CHF durable
• Piston clean
• 11" compact
• HK elite
• Rail ready

Cons:

• HK price
• SBR rules

H&K MR556A4 Upper.

H&K 51000385

"Heckler and Koch (HK USA) MR556A4 UPPER KIT 5.56MM 11\" 51000385 HK51000385." H&K HK51000385 mr556 might. Upper might.

Barrel boss.

The End