Military ballistics is a messy topic. If you’ve spent any time on range forums or watching tactical YouTube, you’ve probably heard a million different opinions on what makes a "sniper" round actually work. Usually, people jump straight to talking about "hollow points" or "fragmentation," assuming that the classic sniper full metal jacket (FMJ) is just some relic of the past or a cheap practice round.
That's a mistake.
Standard FMJ rounds, often called "ball" ammunition, are the backbone of military operations. But there is a massive gap between the bulk-surplus stuff you buy for $0.50 a round and the precision-engineered projectiles used by long-range specialists. Honestly, most folks don't realize that "Full Metal Jacket" describes a construction method, not a performance standard.
What is a Sniper Full Metal Jacket Anyway?
At its simplest, an FMJ is just a lead core swaged inside a harder metal "jacket," usually a copper alloy like gilding metal. The jacket covers everything except, typically, the base. In civilian circles, we call this "range ammo." In the military, it’s 7.62x51mm NATO M80.
But snipers don’t usually use M80.
When we talk about a sniper full metal jacket, we are usually referring to "Open Tip Match" (OTM) ammunition like the legendary M118LR or the .330 Winchester Magnum. Here is where it gets confusing: an OTM looks like a hollow point. It has a tiny hole at the tip. However, under the Hague Convention of 1899, these are legally classified as FMJs in a military context. The hole isn't there to make the bullet expand like a hunting round; it’s a byproduct of the manufacturing process where the jacket is drawn from the base toward the nose to ensure the base is perfectly flat and balanced.
Balance is everything. If the base of the bullet is uneven by a fraction of a millimeter, the gases pushing it out of the barrel will escape unevenly the moment it leaves the muzzle. This "muzzle tip" can throw a shot off by inches at 800 yards.
Physics Doesn't Care About Your Feelings
Long-range shooting is basically a math problem where the wind is trying to make you fail.
A heavy sniper full metal jacket projectile needs a high Ballistic Coefficient (BC). Think of BC as how "slippery" the bullet is in the air. A low BC bullet is like throwing a ping-pong ball; a high BC bullet is like throwing a dart.
Take the Sierra MatchKing 175-grain HPBT (Hollow Point Boat Tail). It’s the gold standard for the M118LR round used by US Marine scouts and Army snipers. Even though it has "hollow point" in the name, it functions as a non-expanding FMJ. The "Boat Tail" is that tapered rear end that reduces base drag. Without that taper, the vacuum created behind the bullet in flight would suck it backward, slowing it down and making it succumb to gravity sooner.
It’s about stability.
Transonic flight is the nightmare. When a bullet slows down from supersonic (faster than sound) to subsonic, it passes through a "transonic" zone. This creates turbulence. A cheap FMJ might tumble here, turning a precise shot into a random guess. A high-quality sniper-grade jacketed round is designed to remain stable through that "buffeting" phase.
Why the Military Sticks to Jacketed Rounds
You might wonder why they don't just use expanding hunting bullets. After all, they’re more "effective" on target, right?
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International law is the big reason. The Hague Convention—which the US follows even though we didn't technically sign that specific part—prohibits bullets that "expand or flatten easily in the human body." This was meant to prevent the horrific wounds caused by early lead-nose bullets.
By using a sniper full metal jacket, militaries stay within legal bounds while focusing on two things:
- Penetration: A jacketed round is much better at punching through light cover, glass, or heavy clothing without veering off course.
- Consistency: It is much easier to mass-produce a highly accurate FMJ than an expanding bullet that maintains perfect balance.
The Myth of the "Clean" Through-and-Through
There’s this weird myth that an FMJ just zips through a target like a needle. "It’s too powerful," people say. "It goes right through and doesn't stop them."
While "over-penetration" is a real thing, it’s not that simple. When a long, heavy sniper full metal jacket round hits tissue at high velocity, it doesn't stay straight. Because the base is heavier than the nose (the "center of gravity" is behind the "center of pressure"), the bullet wants to flip. This is called "yawing."
When the bullet yaws 180 degrees, it creates a massive temporary cavity. If it’s moving fast enough—usually over 2,200 feet per second—the stress of that flip can cause the jacket to rupture at the cannelure (the little groove in the middle). The result is fragmentation that looks a lot like an expanding round, even though it started as a solid "ball" projectile.
Real World Examples: M118LR vs. M80
If you put a standard M80 ball round and an M118LR sniper round next to each other, they look nearly identical to the untrained eye. They are both 7.62x51mm. They both have copper jackets.
But the performance gap is staggering.
- M80 Ball: Generally expected to shoot about 2 to 3 MOA (Minutes of Angle). At 800 yards, that means your "group" could be 24 inches wide. You aren't hitting a specific target; you're hitting an area.
- M118LR (Sniper FMJ): This is expected to be 1 MOA or better. At that same 800 yards, the group is 8 inches or less.
That difference is why snipers are so protective of their "dope" (Data on Previous Engagements). They aren't just shooting a gun; they are managing a specific lot of ammunition that has been tested for consistency. Even the temperature of the powder inside that jacketed round matters. Hot powder burns faster, creating more pressure, which means the bullet leaves the barrel faster and hits higher.
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Common Misconceptions You'll See Online
Don't believe everything you read on Reddit.
One common lie is that FMJs are "illegal" for civilian use. Totally false. They are the most common rounds on earth. Another is that "Full Metal Jacket" means it can pierce armor. Nope. Most FMJs have a soft lead core. To pierce armor, you need an "Armor Piercing" (AP) round, which has a hardened steel or tungsten core inside that jacket.
Then there is the "Green Tip" M855. People call this a sniper round. It isn't. It’s a combat round designed to punch through a steel helmet at 500 meters. It’s actually notoriously inaccurate because the steel "penetrator" tip inside the jacket is often slightly off-center, making the bullet wobble like a bad tire on a car.
Getting Serious: What You Should Actually Use
If you're getting into long-range precision, don't waste your money on bulk surplus FMJ. You'll just get frustrated. You'll think you’re a bad shot when, in reality, your ammo is just incapable of holding a group.
Look for "Match" grade ammunition. Companies like Federal (Gold Medal Match) or Hornady (ELD Match) produce what is essentially a sniper full metal jacket in all but name. These use heavy jackets with extremely thin walls to ensure uniform weight distribution.
Tactical Advice for the Range:
- Check your twist rate: A heavy 175-grain sniper round needs a faster "twist" in your barrel (like 1:10) to stabilize. If you try to fire it through a 1:12 twist barrel, it’ll "keyhole," hitting the paper sideways.
- Chronograph everything: If you want to be a "sniper," you need to know exactly how fast your rounds are going. A jacketed round's speed can vary based on your barrel length and even the humidity.
- Clean your copper: Jacketed rounds leave copper "fouling" inside your barrel. Too much buildup will ruin your accuracy. Use a dedicated copper solvent every couple hundred rounds.
The Bottom Line
The sniper full metal jacket isn't just a basic bullet. It’s a piece of precision machinery. It balances the legal requirements of warfare with the brutal physics of external ballistics. Whether it’s the OTM design of a .300 Win Mag or the classic heavy-grain 7.62, the goal is always the same: predictability.
In the world of long-range shooting, the best bullet isn't the one that hits the hardest; it's the one that does exactly the same thing every single time you pull the trigger.
Next Steps for Implementation:
Start by identifying your rifle's barrel twist rate to match the appropriate grain weight of jacketed ammunition. Purchase three different brands of "Match" grade FMJ or OTM rounds—specifically looking for 168gr or 175gr for .308/7.62 platforms—and conduct a "ladder test" at 100 yards to see which specific jacket construction your barrel prefers before attempting long-range holds.