Whether you’re stacking coyotes and hogs, a law enforcement officer on duty, or defending what’s yours, performance isn’t negotiable.
The M855 green tip and Mk318 have been the standard for decades, each with its own strengths. But let’s be honest—they’re not perfect. The M855 punches through barriers but lacks reliable stopping power. The Mk318 expands better but isn’t the ultimate solution.
Enter the HOP Munitions 62-grain Solid Copper REX. Built to outperform both, this round delivers devastating energy transfer, accuracy, and barrier-blind performance—without the downsides of traditional loads.
M855 Green Tip: The Military Workhorse
The M855, widely recognized as the “green tip,” is a 62-grain full metal jacket round featuring a steel core. Designed for military use, its primary advantage is penetration, making it effective against lightly armored targets. Key specifications include:
- Muzzle Velocity: 3,020 fps
- Muzzle Energy: 1,255 ft/lbs
- Ballistic Coefficient: ∼.304
While the M855’s steel core enhances penetration, its terminal performance can be inconsistent. Fragmentation is unreliable, and expansion is minimal, limiting its effectiveness for hunting or applications where immediate stopping power is critical.
Mk318: The “Silver Bullet”
The Mk318 Mod 0, often referred to as the “Silver Bullet,” was developed to overcome the M855’s shortcomings. Extensively used by the USMC, this open-tip match (OTM) round offers:
- Muzzle Velocity: ∼2,920 fps
- Muzzle Energy: ∼1,186 ft/lbs
- Ballistic Coefficient: ∼.300
The Mk318’s open-tip design facilitates controlled expansion and fragmentation, significantly improving lethality without sacrificing accuracy. However, advancements in ammunition technology have driven the need for even more refined options for tactical, hunting, and duty applications.
Introducing the Next Generation: HOP Munitions 62-Grain Solid Copper REX (Rapid EXpanding)
Taking cues from the proven performance of the Mk318, we’ve pushed the limits even further with our 62-grain Solid Copper REX (Rapid EXpanding) round. Designed to outperform both the M855 and Mk318, it boasts:
- Muzzle Velocity: 2,870 fps
- Muzzle Energy: 1,134 ft/lbs
- Ballistic Coefficient: .300
- Sectional Density: .177
These specs translate into deep penetration, devastating knockdown power, and exceptional accuracy—making this round ideal for law enforcement, military, coyote and hog hunting, and home defense.
Key Advantages of the Solid Copper REX
Superior Stopping Power
The Solid Copper REX is engineered for controlled expansion and consistent energy transfer. Compared to the M855’s steel core and the Mk318’s open-tip design, the REX delivers significantly more reliable terminal ballistics. It is the ideal choice for duty use where stopping power is necessary.
Exceptional Precision
With a ballistic coefficient of .300, the REX provides a flat trajectory and excellent wind resistance, ensuring accurate shot placement at extended ranges—critical for law enforcement marksmen and military professionals.
Eco-Friendly and Durable
Made entirely from solid copper, the REX eliminates lead contamination while maintaining extreme durability. It reliably penetrates barriers without structural failure, making it ideal for duty and tactical scenarios.
Versatility Across Applications
Thanks to its high velocity and energy transfer, the REX is ideally suited for hunting small-to-medium game, home defense, and professional use by law enforcement and military personnel.
Closing the Gap on the 77-Grain OTM
Tier 1 military units have long favored the 77-grain Open-Tip Match (OTM) round for its accuracy and devastating terminal performance. Its heavier weight provides excellent flight stability, making it a go-to choice for precision shooting. Notable specs include:
- Muzzle Velocity: ~2,750 fps
- Muzzle Energy: ~1,293 ft/lbs
- Ballistic Coefficient (G1): ~0.370 to 0.380
The 77-grain OTM’s boattail and open-tip design contribute to its superior long-range performance. However, to maximize stabilization, it requires a 1:7 or 1:8 twist barrel.
For those committed to 77-grain loads, HOP Munitions also offers a 77-grain HPBT option, delivering the same precision and performance expected from this bullet weight.
That said, for shooters looking for a well-balanced alternative, the 62-grain Solid Copper REX bridges the gap between the lightweight versatility of the M855 and the specialized precision of the 77-grain OTM.
Although lighter than the 77-grain OTM, the REX achieves comparable accuracy and terminal effect, making it a practical choice across various mission requirements.
Why Switch to the 62-Grain 5.56 REX?
If you expect more from your ammunition, the HOP Munitions 62-grain Solid Copper REX is the answer.
Unrivaled Stopping Power
Unlike traditional steel-core or hollow-point rounds, the REX is designed to deliver devastating terminal performance. Upon impact, its solid copper construction ensures consistent expansion, maximizing energy transfer to the target. Whether for hunting, home defense, or duty use, this round provides absolute confidence in its stopping power.
Accuracy
With a ballistic coefficient of .300, the 62-grain REX offers superior stability and flat-shooting performance—even in wind or at extended ranges. It cuts through barriers and maintains accuracy.
Environmentally Friendly and Light Barrier Penetration
The REX’s solid copper build eliminates lead exposure and enhances durability. It can penetrate light barriers such as auto glass, plywood, and sheet metal without sacrificing structural integrity, ensuring consistent results.
Mission-Ready Versatility
Whether you’re a predator hunter operating in open fields or a law enforcement professional engaging on duty, the 62-grain solid copper REX is up to the task.
Final Thoughts
The 62-grain REX surpasses legacy loads like the M855 and Mk318 in energy transfer and terminal performance while delivering accuracy comparable to heavier 77-grain OTM—all in a lighter, faster package.
If you’re looking for ammo that hits harder, shoots flatter, and performs flawlessly—the HOP Munitions 62-grain REX is the answer.
Stop settling for “good enough.”
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