250 Rounds Black Hills Ammunition Factory New D556N9 - 5.56 NATO 77 Grain Hollow Point OTM in 50 round boxes

If you read our review of the MK 262 MOD 1-C (SKU: MP460556N9) and wondered how it differs from Black Hills’ standard commercial 77-grain OTM boxes, you are looking at the answer. The D556N9 is Black Hills' primary commercial line of heavy-combat 5.56mm, typically sold in standard 50-round yellow boxes. It offers the exact same blistering velocity and powder charge as the legendary military round but features a distinct, updated bullet lineage.

Overview & Technical Specifications

While the MK 262 military line strictly utilizes the Sierra MatchKing projectile, Black Hills updated the D556N9 commercial line to feature a custom 77-grain OTM projectile manufactured exclusively for Black Hills by Hornady. This custom bullet was meticulously engineered to mirror the exact jacket thickness, weight distribution, and ballistic coefficient of the original Sierra design, delivering identical external and terminal ballistics.

• Caliber: 5.56x45mm NATO (High-pressure load; not for .223 Remington chambers)

• Bullet Weight: 77 grain

• Bullet Type: Open Tip Match (OTM) with cannelure (Custom Hornady production)

• Casing: New brass (Lake City origin), factory annealed, boxer-primed, reloadable

• Muzzle Velocity: ~2,750 ft/s (from a 20-inch test barrel)

• Muzzle Energy: ~1,293 ft-lbs

Performance and Ballistics

1. The Twin to MK 262

In both velocity testing and real-world accuracy, the Hornady-made 77gr OTM projectile in the D556N9 performs virtually indistinguishably from its Sierra MatchKing brother. Fired out of an accurate barrel, this round routinely shoots sub-MOA or even half-MOA groups. It features the exact same military-spec flash-suppressed powder charge, offering identical point-of-impact behavior if you use it interchangeably with military-surplus MK 262.

2. High Ballistic Coefficient & Wind Resistance

The core advantage of the heavy 77-grain OTM profile is how it handles the elements. Standard 55-grain M193 rounds lose velocity rapidly and get easily pushed around by crosswinds at long distances. The D556N9 maintains its momentum significantly better, slicing through wind and maintaining a predictable, flat trajectory out to 600 yards and beyond.

3. Devastating Short-Barrel Terminal Performance

Though it is technically a "Match" bullet designed for precision, the OTM construction handles tissue phenomenally well. Upon impact, the bullet is designed to destabilize, yawn, and fragment violently at the cannelure. Because it is a heavy bullet moving at 5.56 NATO pressures, it retains enough velocity to fragment reliably even when fired out of short-barreled rifles (SBRs) like a 10.3-inch or 11.5-inch barrel, making it a favorite for close-quarters defensive setups.

Pros & Cons

Pros

• Match-Grade Precision: Easily ranks among the most inherently precise mass-produced 5.56mm factory cartridges on earth.

• Seamless Military Clone: Gives you true MK 262 performance, velocity, and trajectory without having to track down restricted military lots.

• Excellent SBR Ballistics: Performs better terminally out of short barrels than standard 55gr or 62gr ammunition.

• Premium Brass: Uses premier Lake City brass with visible factory annealing at the neck for enhanced durability and reloadability.

Cons

• Strict Twist Requirements: The long 77-grain bullet absolutely requires a 1:7" or 1:8" twist barrel to stabilize. Shooting this through a slower 1:9" twist rifle can result in unstable flight and bullet tumbling.

• Premium Pricing: Typically sold in 50-round boxes, the high cost per round makes it a luxury choice best reserved for precision training, long-range matches, or duty storage rather than high-volume casual plinking.

The Verdict

The Black Hills D556N9 (77gr OTM) is a masterpiece of precision and power. By blending their proprietary tactical loading secrets with an elite, custom-tailored Hornady projectile, Black Hills provides civilian shooters with flawless, combat-ready match ammunition that pushes the AR-15 platform to its absolute limits.

• The Takeaway: AI can sometimes make mistakes, but it's never a mistake to order from Eagle Eye Guns.