Description
| Manufacturer | Heckler & Koch |
|---|---|
| Caliber | 5.56x45mm NATO |
| Primary Role | CQB / Vehicle Operations / Entry Team Platform |
| Operating System | Short-Stroke Gas Piston |
| Barrel | 11″ Cold Hammer Forged (CHF), Heavy Contour |
| Controls | Fully Ambidextrous (A4 Configuration) |
| Handguard | Free-Floating M-LOK System |
| Classification | SBR (Short Barreled Rifle) – NFA Rules Apply |
The Pinnacle of Compact Piston-Driven Performance
The HK MR556-A4 11″ SBR represents the latest evolution in the renowned 5.56mm piston-driven lineage. The “A4” generation brings the platform to true parity with modern tactical requirements, featuring fully ambidextrous controls and enhanced modularity. As an authorized government provider, PAI Defense ensures that these mission-critical, NFA-regulated systems are delivered with the highest level of compliance, auditing, and administrative precision required for state and federal procurement.
Advanced Technical Architecture
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Short-Stroke Gas Piston System: Operates on HK’s legendary piston mechanism, which prevents hot carbon and combustion gases from entering the receiver. This ensures the weapon runs exceptionally clean and cool, maximizing reliability under high firing cadences or when deployed with a suppressor.
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A4 Ambidextrous Upgrades: The latest A4 configuration introduces fully ambidextrous operating controls, including the bolt catch/release, magazine release, and safety selector, allowing seamless manipulation from either shoulder in confined environments.
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Precision Cold Hammer Forged Barrel: Equipped with an 11-inch, thick-contour cold hammer-forged barrel that provides exceptional accuracy and thermal stability, ensuring the platform performs consistently even during sustained engagements.
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Modern Interface: Features a free-floating M-LOK compatible handguard, providing a rigid, low-profile mounting surface for advanced optics, laser aiming modules, and tactical illumination systems.
PAI Defense: Your Authorized HK Procurement Partner
Navigating government acquisitions for NFA-regulated items requires a strategic B2B approach. PAI Defense provides the corporate verbiage, audited technical specifications, and streamlined RFP processes necessary to support procurement officers. Beyond initial acquisition, our status as an authorized HK distributor guarantees long-term sustainability through direct access to OEM replacement parts, magazines, and technical support, ensuring your agency’s fleet remains mission-ready.









