HOP Munitions 62-Grain Solid Copper REX vs. M855 Green Tip and Mk318

Selecting the right 5.56 load is critical—it could be the edge you need in the field or on duty.

The M855 green tip and the Mk318 have been trusted staples for decades, each offering distinct advantages.

However, our new 62-grain Solid Copper REX (Rapid EXpanding) ammo is here to redefine the standard, delivering unmatched accuracy, energy transfer, and stopping power.

M855 Green Tip: The Workhorse of the Military

The M855, commonly known as the “green tip,” is a 62-grain full metal jacket with a steel core. Developed for the U.S. military, its design prioritizes penetration, making it effective against lightly armored targets. Key specs include:

• Muzzle Velocity: 3,020 fps
• Muzzle Energy: 1,255 ft/lbs
• Ballistic Coefficient: ∼.304

While the M855’s steel core offers enhanced penetration, its terminal ballistics often fall short, with inconsistent fragmentation and minimal expansion upon impact. This limits its effectiveness for hunting or scenarios requiring reliable stopping power.

Mk318: The “Silver Bullet”

Nicknamed the “Silver Bullet,” the Mk318 Mod 0 was developed to address the shortcomings of the M855. Used extensively by the USMC, this open-tip match (OTM) round features:

• Muzzle Velocity: ∼2,920 fps
• Muzzle Energy: ∼1,186 ft/lbs
• Ballistic Coefficient: ∼.300

The Mk318’s open-tip design promotes controlled expansion and fragmentation, improving lethality while maintaining excellent accuracy. However, as technology evolves, so does the demand for even more advanced ammunition tailored for hunting, tactical applications, and duty use.

Enter the Next Generation: HOP Munitions 62-Grain Solid Copper REX (Rapid EXpanding)

We have taken inspiration from the legendary Mk318 and pushed the boundaries further with the 62-grain Solid Copper REX (Rapid EXpanding) ammo. Built to exceed the capabilities of both the M855 and Mk318, this round offers:

• Muzzle Velocity: 2,870 fps
• Muzzle Energy: 1,134 ft/lbs
• Ballistic Coefficient: .300
• Sectional Density: .177

These impressive specs translate to deep penetration, devastating knockdown power, and exceptional accuracy—perfect for law enforcement, military, coyote, hog hunts, and home defense scenarios.

Key Advantages of the Solid Copper REX

1. Enhanced Stopping Power
   • The Solid Copper REX bullet design ensures controlled expansion and consistent energy transfer, making it more effective than the M855’s steel core and the Mk318’s open-tip design. This makes it ideal for duty use where reliable stopping power is crucial.
2. Precision Performance
   • With a ballistic coefficient of .300, the REX offers flat trajectories and improved wind resistance, ensuring on-target performance even at extended ranges, a critical factor for law enforcement marksmen and military operators.
3. Eco-Friendly and Durable
   • As a solid copper bullet, the REX eliminates lead contamination while providing exceptional structural integrity, ensuring reliable performance through barriers—a necessity in duty and tactical operations.
4. Versatility for Hunting, Defense, and Duty
   • The combination of high velocity and energy transfer makes this round equally suited for small-to-medium game hunting, home defense, and service use by military and law enforcement personnel.

Closing the Gap on 77-Grain OTM

The 77-grain Open-Tip Match (OTM) round has long been a favorite among Tier 1 military units for its exceptional accuracy and terminal performance. Its heavier weight allows it to maintain stability in flight, resulting in consistent accuracy across varying distances. Key specifications of the 77-grain OTM include:

• Muzzle Velocity: ~2,750 fps
• Muzzle Energy: ~1,293 ft/lbs
• Ballistic Coefficient (G1): ~0.370 to 0.380

The pointed open-tip and boat-tail design of the 77-grain OTM contribute to its long-range performance and flight stability, making it a top choice for precision shooting and competition. A 1:7 or 1:8 twist barrel is generally recommended to stabilize these heavier bullets effectively.

For those hard set on shooting 77-grain rounds, HOP Munitions also offers a 77-grain HPBT load that delivers the same exceptional performance expected of this bullet weight.

However, for shooters looking for a versatile alternative, the HOP Munitions 62-grain Solid Copper REX bridges the gap between the versatility of lighter rounds like the M855 and the specialized performance of the 77-grain OTM.

While lighter than the 77-grain OTM, the REX delivers comparable accuracy and terminal performance, offering a reliable option for various mission sets.

Why Should I Make the Switch to 62-Grain 5.56 REX?

If you demand more from your ammunition, the answer is simple: the HOP Munitions 62-grain Solid Copper REX redefines what a 5.56 round can do.

Here’s why you should make the switch:

1. Uncompromising Stopping Power
   Unlike standard steel-core or hollow-point rounds, the REX is engineered to deliver devastating terminal performance. Its solid copper design expands reliably upon impact, transferring maximum energy to the target and ensuring consistent knockdown power. Whether you’re hunting, defending your home, or on duty, the REX guarantees you’ll never second-guess your round’s effectiveness.
2. Accuracy
   With a ballistic coefficient of .300, the 62-grain REX offers exceptional stability and flat trajectories, even at extended ranges. Wind? Distance? Barriers? The REX shrugs them off and stays on target.
3. Eco-Friendly and Built Tough
   The REX’s solid copper construction is environmentally conscious and incredibly durable. It penetrates light barriers such as auto glass, sheetrock, plywood, or sheet metal while maintaining structural integrity, ensuring consistent performance.
4. Mission-Ready Versatility
   From predator hunting in open fields to tactical applications in urban environments, the REX thrives. Its performance is tailored for law enforcement, military, and serious shooters who refuse to compromise.
5. Proven to Outperform
   The 62-grain REX outclasses traditional loads like the M855 and Mk318 in energy transfer and terminal ballistics, while offering comparable precision to heavier 77-grain OTMs—all in a lighter, faster package. This isn’t just another round; it’s an upgrade for your rifle and your mission.