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.”
5.56×45 and devastating knockdown power.
Uhhh Okay.
Four sixteeny Bawana
Every one warm up the credit card and order some ‘HOP Munitions 62-grain REX’.
????
855 is steel tip and mild steel. Big reason why it can be sold at bass pro as if it was steel core (regardless of hardness) it would be flat out illegal as it would be defacto AP pistol ammo. With that said does great for terminal performance after it goes through barriers or lightweight uhmwpe plates without a ceramic strike face. This new ammo reminds me of a option from Lehigh Defense so may be worth looking into.
I was under the impression that when they amended GCA ’68 back in the 1980s, in order to declare “muh cop killa boolits” Officially Naughty, a specific exemption was added to the text of the law at the last moment to allow the sale of M855 and equivalents to the public.
This was redundant because the new portion pertaining to so-called “armor piercing” ammunition already exempted .22 caliber and smaller projectiles from the new prohibitions. This did not, of course, prevent the Kenyan from ordering surplus M855 ammunition to be dumped in the ocean, and ordering BATFE to regard 5.45x39mm steel-core milsurp as contraband despite the fact that it is closer to .21 caliber than to .22. It was illegal, but he did it, and there were no consequences.
Interesting article, but I want to know what 1000 rds is going set me back.
I’ve got a bunch of Mk318 in storage. I think I’ll stick with that for now as my SHTF ammo. But the Hop 62-grain REX is interesting, I wonder how much for high quantity lots.
I can find out. For now, I know code ‘gearbunker5’ gets you 5% off everything on their website.
Thanks Scott.
I was curious about the price too, did some research, and tried to post the results yesterday. Off to the ether it went! Happens a lot, as noted by many others.
Trying differently. Payne wants a buck seventy per round, before shipping, discounts, and tax. A check on that ammo seek site showed this to be in the middle of the pack for 62 gr monolithic copper hollow point ammo prices. There’s a gun club (gosh, will that phrase pass the filter?????????) out west, that has frog bones in the name, that has it on sale at five hondo for five hondo, regularly seven hondo fitty.
If this one gets ethered, I give up.
There’s that “stopping power” thing again. I’ve been assured time after time, even by articles on this website, that “stopping power” doesn’t exist at all.
Just sayin’.
“There’s that “stopping power” thing again. I’ve been assured time after time, even by articles on this website, that “stopping power” doesn’t exist at all.
Just sayin’.”
You apparently didn’t understand the subject of “stopping power” you were reading about. Basically; No one is saying “stopping power” doesn’t exist, it does or can exist in a practical physical sense in relation to the target. Its just that it doesn’t exist as a quantifiable measure of a round effectiveness because its nebulous for that purpose.
Tully Mud,
The term “stopping power” is a subjective and qualitative term. It refers to the repeatable (e.g. predictable) inherent ability of a firearm-and-ammunition combination to physically (and immediately) incapacitate a human attacker without having to destroy the attacker’s central nervous system.
Note that the only repeatable way to immediately stop a human attacker (without requiring central nervous system damage) is to cause massive trauma which shuts down the human body immediately.
Handguns do not cause such massive trauma on general torso hits thus conventional wisdom informs us that handguns do not have stopping power. On the other hand, most shotguns and centerfire rifles do cause such massive trauma at short ranges thus conventional wisdom informs us that those firearms typically have excellent “stopping power” at close range.
That is how/why some firearm platforms do NOT have “stopping power” (e.g. handguns) and other firearm platforms DO have “stopping power” (e.g. shotguns and rifles).
Capiche?
I’ll my green tip I can’t shoot in ILL annoy. Classic Firearms had video where it defeated #3 body armor.
Just don’t expect it to go through typical steel (even low end ar500) or most anything with a ceramic strike face. It’s fine for a lot of things but actual AP is not one of them outside the poly plates.
Way to tell which one is best is shoot yourself with both…Bet the first one wins.
Sounds like you are speaking from experience Debbie.
🙂
“Eco-Friendly” = all after suspect as total BS
Ok, this may sound like a stupid question… at https://hopmunitions.com/product/556-62gr-rex-50-rounds/ it says this:
“Product Overview
Building on the legendary performance of the MK318—known as the “Silver Bullet” and trusted by the USMC—our 5.56 62-grain Solid Copper REX (Rapid EXpanding) ammo represents the next evolution in precision and stopping power. Designed to surpass the capabilities of its predecessor, this advanced round delivers the perfect balance of accuracy, energy transfer, and controlled expansion, making it the ultimate choice for your next coyote hunt or hog hunt.
With a blistering velocity of 2,870 fps and an impressive energy transfer of 1,134 ft/lbs, the REX boasts an impressive ballistic coefficient of .300 and a sectional density of .177 to ensure deep penetration and devastating knockdown power.
Made with premium primers, powders, and US-made brass, this next-generation “Silver Bullet” is designed to outperform traditional hollow-point bullets. Packaged in boxes of 50, the 62-grain Solid Copper REX sets a new standard in hunting ammunition, delivering uncompromising performance every time you pull the trigger.”
But in the article it says this:
“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.”
The web site doesn’t mention “home defense, or duty use” for this round, only mentions hunting use.
So why the difference?
See, told ya it was a dumb question. But why is “”home defense, or duty use” for this round not mentioned on the web site?
President Trump invokes the Alien Enemies Act of 1798: Invocation of the Alien Enemies Act Regarding the Invasion of The United States by Tren De Aragua.
https://www.whitehouse.gov/presidential-actions/2025/03/invocation-of-the-alien-enemies-act-regarding-the-invasion-of-the-united-states-by-tren-de-aragua/
In other news, President Trump ordered military strikes on Iran-backed Houthi rebels in Yemen – strikes carried out (note: The Houthi rebels been attacking ships in the area including U.S. Navy and commercial ships. They had been previously warned but kept doing it. Of course Iran says “Who us? We didn’t do nuthin.”)
In short, President Trump is not fooling around – if he says ‘stop it!’ that’s just what he means.
Trump Orders Military Strikes Against Houthi Terrorists in Yemen.
https://pjmedia.com/matt-margolis/2025/03/15/trump-orders-military-strikes-against-houthi-terrorists-in-yemen-n4937952
‘Extermination’ site discovered in Mexico with cremation ovens, human remains (used by one of the area’s cartels known as the New Generation Jalisco Cartel.)
“Inside the abandoned ranch’s gates were an increasing number of horrors, including hundreds of pairs of shoes, even children’s toys.”
https://www.foxnews.com/world/extermination-site-discovered-mexico-cremation-ovens-human-remains
See, that’s the result of all of those illegal guns smuggled in from the USA! (As if.)
Serious question: why are these cartel members so incredibly vicious?
Cultural issues, recruitment from military/intelligence units, long term working relationship with the CIA honestly who knows. Only ever saw it matched by some of the worst of ISIS and a bit of the various Chinese mafias.
Mark N.,
Incredibly vicious people are the natural result of people who reject God wholesale and embrace/celebrate evil. That combination leads to a depraved mind where anything goes.
………. honestly this over mine even if mine may also apply.
Hunter Biden, Beset by Legal Woes, Flees to… South Africa?
“Poor Hunter Biden. First, his meal ticket father leaves office and disappears from public view (for which blessing many of us are breathing a sigh of relief), then his California house burns up, along with a bunch of his “priceless” art. The guy just can’t catch a break.
On Saturday, we learned that Hunter’s woes are worsening. He was facing an uncomfortable deposition in California, but a kindly judge allowed that case to be dismissed as Hunter’s too broke to continue. So now the poverty-stricken former First Son has jetted off to Cape Town, South Africa, accompanied by his Secret Service retinue, to suffer from his poverty in a $500/night beachfront villa.
…”
https://redstate.com/wardclark/2025/03/15/hunter-biden-beset-by-legal-woes-flees-to-south-africa-n2186704
$500 a night ain’t to damn broke.
I’m a nice guy, I only charge $45 a night for my riverside cabin.
No one has wound up dead there ,,,,,,,Yet.
Do Armed Civilians Really Stop Mass Shootings? This Study Has the Answer.
https://www.usacarry.com/do-armed-civilians-really-stop-mass-shootings/?utm_source=emailoctopus&utm_medium=email&utm_campaign=Newsletter%203%2F15%2F2025
UPDATED 2: A Deep Dive into Cases Where Civilians Stopped Active Shooters. Did they accidentally shoot bystanders, get in the way of police, get their gun taken away, or create other problems? How does it compare to police who stopped these attacks?
https://crimeresearch.org/2025/02/a-deep-dive-into-cases-where-civilians-stopped-active-shooters-did-they-accidentally-shoot-bystanders-get-in-the-way-of-police-get-their-gun-taken-away-or-more/
Seriously…did he really say that M855 has a “steel core”?
You would think that someone who makes a living writing about guns and ammo…would have some actual knowledge on the subject.
The M855 Ball (‘green tip’) military spec, for the bullet, is 4 g (62 gr) FMJ (Copper) Boat-Tail with Steel Penetrator and Lead Core. So, no, it does not have a steel core but rather a lead core and a steel penetrator.
Interestingly the newer 855a1 is also a steel tip but with a copper (formerly other stuff as well) core and similarly is not an AP ammo. Bitch to find it in meaningful quantities and expensive when you do but it will zip through most any steel plate a person can wear and most lv3/rf1-2 armors that do not have a good enough ceramic strike face. Pain in the ass to find reloading data for it or it’s 308 equivalent though.
So, to me I understand the new ammo is probably good, but what is the price? Makes no sense if it’s not affordable. Cost for 1000 round count?
$85 for 50 rounds. Says House of Payne on the box. Works out to $1700 for a thousand. Which you probably won’t need unless you are stocking up for life or for war. This ain’t no plinkin’ ammo. (At least not on my budget.)
I’d like to see a picture of an expanded bullet.
Yup. I assume it peels back resulting in four long petals.
I have a few hundred rounds od .308 steel core. Ill take that over the little bullets.
A sheet metal screw and a hollow point.
Over a dollar per round.
And no actual evidence presented of better performance.
Not even a photo of an expanded round.
No thanks