7.62x39 vs. 7.62x51: What’s the Difference Between These Same Caliber Cartridges?

The 7.62x39 vs. 7.62x51 debate is uncommon. Shooters familiar enough with the rounds to compare them already know they are extremely dissimilar (despite sharing the same caliber projectile).

It’s not an apples-to-apples comparison, but “7.62x39 vs. 7.62x51” is comparable to “223 Rem vs. 308 Win.” In both cases, the former is an intermediate battle cartridge, whereas the latter is intended for sniping over longer distances.

We’re not comparing these cartridges because they’re similarly powerful, or share similar applications. We’re comparing them because they’re so similarly named. People confuse the two, or suppose they must be more similar than they actually are due to 39’s nearness to 51.

Here’s why the 7.62x51 and 7.62x39 are really different from one another.

The Differences Between 7.62x39 and 7.62x51

In this article, we’ll be discussing the differences between the 7.62x39mm and 7.62x51mm NATO in terms of real-world performance: recoil, trajectory, stopping power, and more. We’ll conclude by declaring a “winner.”

Before we dig into performance, let’s review the cartridges’ physical differences. Just placing the two side by side illustrates a whole lot.

Cartridge Specs

The 7.62x39 and 7.62x51 are both rimless bottleneck cartridges. The 7.62x39 is a unique design originating in the Soviet Union in 1943. The 7.62x51’s parent case is the T-65 experimental cartridge, which came from the .300 Savage and .30-06 Springfield.

The 7.62x39 is odd for having a range of accepted bullet diameters. The Sporting Arms and Ammunition Manufacturers Institute (SAAMI) sets its bullet diameter ranging from 0.309-0.311”, whereas the Permanent International Commission for the Proof of Small Arms (C.I.P.) sets it at 0.312”. The 7.62x51 keeps it simple with a true bullet diameter of 0.308”.

The 7.62x51 has a larger neck diameter (0.345”) and base diameter (0.470”) than the 7.62x39 (0.339” neck diameter and 0.447” base diameter).

The 7.62x39's case length is 1.524”, whereas the 7.62x51's is almost half an inch longer, at 2.015”. This difference accounts for the two rounds’ different names, as “39mm” and “51mm” correspond to their case lengths (albeit inexactly). Its longer case extends the 7.62x51's overall length to 2.800”, compared to 2.205” for the 7.62x39. This results in a case capacity of 52.0 grains H₂O for the 7.62x51 and 35.6 grains H₂O for the 7.62x39.

These rounds have very different maximum pressures. The 7.62x39 is 45,010 psi (according to SAAMI); the 7.62x51, 60,191 psi (according to NATO).

Now that we’ve covered each cartridge's basic specs, let’s see how they affect real-world performance.

Recoil: 7.62x39mm vs. 7.62x51mm

I always compare recoil because it’s one of the first things a shooter asks about. We all want to know how much it kicks – not so much because of physical pain (though this can be an issue), but more so for initial accuracy and follow-up shots. A cartridge with more felt recoil kicks the muzzle off the target more with each shot, thus slowing follow-up shots and possibly causing the shooter to flinch.

The less recoil you feel, the more accurately you can fire. Less is always better (unless you’re a macho man who has to prove how tough you are to the world). “Felt” recoil is subjective, as it varies from shooter to shooter. That’s why we base our comparison on free recoil energy. It’s an objective measure of recoil determined by four variables: projectile weight, propellant weight, muzzle velocity, and firearm weight.

Knowing this, we can predict that the 7.62x51’s heavier and higher-velocity projectile will give it substantially more recoil – but how much? Let’s find out.

When firing an 8-pound rifle, the 7.62x51 generates approximately 22 ft-lbs of recoil – roughly 2.5X as much recoil as the 7.62x39 (8.7 ft-lbs).

The 7.62x39 wins this section. It has less recoil, it’s easier to control, and it’s altogether more comfortable to fire.

Trajectory

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A bullet’s trajectory is the path it takes upon exiting the muzzle. We measure trajectory in terms of bullet drop and rise. When graphed out, drop and rise give a trajectory its profile.

A flat trajectory is preferred for firing across longer distances, as it requires the shooter to make fewer adjustments to remain accurate.

A cartridge's trajectory varies from load to load, so the following scenarios are generalizations.

A 7.62x39mm 123 grain bullet with a muzzle velocity of 2,075 fps sighted in at 100 yards will drop -23.8” at 300 yards.

A 7.62x51mm 149 grain bullet with a muzzle velocity of 2,790 fps sighted in at 100 yards will drop -13.4” at 300 yards.

The 7.62x51 has a much flatter trajectory. It’s only evident over longer distances, but it’s still prominent enough to easily win this category.

Accuracy: 7.62x51mm vs. 7.62x39mm

It’s crucial to remember that accuracy is more often a function of the shooting platform and the shooter than of the cartridge itself. The ammo, the rifle, environmental conditions, and the shooter all play significant roles in determining how much accuracy a cartridge can exhibit.

For the sake of argument, we’ll only consider the cartridges' trajectories and recoil. That makes this section a tie, as the 7.62x39 has less recoil, and the 7.62x51 has a flatter trajectory.

At close distances (i.e. within 200 yards), you’ll likely be more accurate with the 7.62x39, whereas long-range shooters will be more accurate with the 7.62x51.

Ballistic Coefficient

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Ballistic coefficient (BC) reflects how effectively a bullet resists wind deflection and frontal air resistance. In other words, it’s a numeric representation of how aerodynamic a bullet is. A higher BC is preferable for long-distance shooting, as it indicates a bullet that will exhibit a more predictable trajectory.

Generally, a heavier, sleeker bullet has a higher BC, as it takes more force to disrupt its flight than a lighter, blunter projectile.

7.62x39mm projectiles typically have a G1 BC ranging from 0.225 to 0.325.

7.62x51mm projectiles typically have a G1 BC ranging from 0.393 to 0.450.

Because the 7.62x51mm fires heavier bullets, it has a higher BC than the 7.62x39mm. The 7.62x51 wins this section.

Stopping Power: 7.62x39mm vs 7.62x51mm NATO

“Stopping power” is tricky to define. It means different things to different shooters. To further complicate the issue, shot placement is more important than stopping power. A poorly placed shot from a cartridge with more “stopping power” can easily be less effective than a well-placed shot from a weaker round.

For the sake of time, let’s agree that stopping power is determined by penetration depth, size of the hole created (aka wound column diameter), and kinetic energy transfer. Taking this into account, the 7.62x51 has more stopping power than the 7.62x39. It fires heavier projectiles at higher velocities. It typically penetrates deeper and transfers more kinetic energy to its target as well.

Hunting

The 7.62x51 has similar ballistics to the .308 Winchester (they are extremely similar cartridges, so much so that SAAMI doesn’t consider it unsafe to treat them interchangeably), one of the most popular hunting cartridges in the U.S.

The 7.62x39 is comparable to the .30-30 Winchester, another solid deer hunting cartridge. The 30-30 is nowhere near as powerful as the 308 Win, however. It does well on whitetail within the shorter distances conventionally associated with dense woodland, although it isn’t an advisable choice for larger elk and moose. Though some might argue that the 308 Win is also too little for large game, it is a far better choice than the 30-30.

The 7.62x39 is fine for taking deer and swine within 100-150 yards, but the 7.62x51’s ability to drop the same at 500+ yards makes it a far more impressive hunting cartridge. We have to award it this section. It’s just more versatile.

Cost & Availability

Don’t choose a cartridge until you understand what rifle and ammo prices are going to do to your wallet.

The 7.62x51 has a higher overall cost; rifles and ammo tend to be more expensive. There are fewer options when it comes to 7.62x39 firearms, and specialized hunting ammo isn’t as common. But at the end of the day, it is cheaper, and it’s about as easy to find as 7.62x51 and 308 Win.

Reloadability

Reloading is an excellent way to craft the perfect round for your firearm and save a little money in the process. Most people are deterred by the initial investment in supplies and equipment. However, you can create higher-quality ammo for less and enjoy total control over most of the process.

Both cartridges are reloadable, but you might have an easier time finding supplies for the 7.62x51 since it’s nearly identical to the .308 Win.

This section is a tie because both cartridges are reloadable.

What are the Ballistic Differences Between 7.62x39mm and 7.62x51mm Cartridges?

The team at Ammo.com has gathered ballistic data for each cartridge for you to compare.

7.62x39 Ballistics

Note: This information comes from the manufacturers. The actual ballistic data obtained with your firearm can vary considerably from the advertised ballistics. Also, ballistics can vary from lot to lot with the same brand and type load.

Take a deeper dive into 7.62x39 ballistics.

7.62x51 Ballistics

Brief History of 7.62x39mm

Near the end of WWII, the Soviet Union decided to develop an intermediate cartridge for its new battle rifle. This cartridge would suit various firearms, from semi-auto carbines for close-range to fully automatic machine guns for suppressive fire.

Hundreds of designs were submitted, but Russia settled on 57-N-231, which had cartridge dimensions of 7.62x41mm.

The first bullet was not a boat tail design, as the Soviet cartridge designers incorrectly assumed that a boat tail design was best only for long-range shots. The designer's assumption that all combat would be held at close range led them to this decision.

After extensive testing, they determined that the boat tail also increased close-range accuracy, and a new boat tail bullet was adopted. This longer bullet required reducing the cartridge case to 39mm. Thus the 7.62x39mm was born.

The 7.62x39 was adopted for the semi-automatic SKS and Mikhail Kalashnikov’s AK-47. The AK-47 became the most mass-produced military rifle, and the 7.62x39 contributed to its success.

The 7.62x39 was one of the Cold War's most prevalent and combat-effective rifle cartridges. It remains extremely popular for warfare, and probably will for as long as warfare involves rifles.

Brief History of 7.62x51mm NATO

Despite having a nomenclature similar to that of the 7.62x39mm, Russia did not develop the 7.62x51mm NATO rifle cartridge.

In the 1950s, America created the M14 and 7.62x51mm to replace the M1 Garand and .30-06 Springfield. The 7.62x51 was used in various firearms, including bolt-action sniper rifles, semi-automatic rifles, and machine guns.

Winchester saw the potential for civilian use, and it developed the .308 Winchester based on the 7.62x51mm. The .308 Winchester has a marginally shorter headspace and thinner case walls than the 7.62x51mm. This means 7.62x51mm NATO can reliably feed and fire in rifles chambered for .308 Win.

The .308 Winchester remains a popular round among American civilian hunters and shooters, but the 7.62x51mm NATO doesn’t have that same kind of following. It’s widely used by NATO countries, though, and probably will be for as long as NATO still exists.

Wes Littlefield

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