.308 Win vs 7.62x51 NATO: Are They the Same Cartridge?

.308 Winchester and 7.62x51 NATO share the same outside case dimensions, and you will find both on the same shelf. The two rounds follow different standards. SAAMI caps .308 Win at 62,000 psi. NATO caps 7.62x51 at 415 MPa, about 60,190 psi, according to Primary Arms.

GunUniversity, Primary Arms, and the NRA's Shooting Sports USA all state you are safe to fire 7.62x51 NATO in a rifle chambered for .308 Win. The reverse direction draws more caution.

A 7.62 NATO chamber allows about 0.008 inches more headspace than the SAAMI .308 Win spec, per Glen Zediker in Shooting Sports USA. Commercial .308 brass has thinner walls, so a .308 case fired in a loose military chamber stretches more.

SAAMI does not list the combination as unsafe, yet GunUniversity advises you never fire .308 Win in a rifle marked 7.62x51 NATO.

Follow your rifle maker's guidance.

308 Winchester and 7.62x51 NATO are closely related cartridges with the same case length and very similar external dimensions, but they are governed by different standards and specifications.

The 308 Winchester uses SAAMI commercial standards and is listed with slightly higher maximum chamber pressure and case capacity, while 7.62x51 NATO follows military EPVAT standards and typically uses thicker cases with somewhat less internal capacity.

Their common FMJ loads are very similar in velocity and muzzle energy, so practical performance is close, but differences in chamber dimensions, headspace, and pressure specifications are important when evaluating firearm compatibility.

Winchester introduced the .308 in 1952 as the commercial version of the 7.62x51mm NATO cartridge.

The round became the dominant hunting and precision rifle cartridge in North America. The 2.015-inch case fits short-action bolt guns and AR-10 and M1A semi-automatic platforms.

Short actions run lighter and stiffer than long actions, which aids accuracy and trims rifle weight. MeatEater measured a Federal Trophy Copper 165-grain load at about 2,700 fps and 2,671 ft-lbs of muzzle energy.

Moderate recoil and consistent accuracy made the .308 a staple for various game hunting, tactical use, and competition shooting.

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Nosler Ballistic Tip, AccuBond, and Partition

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7.62x51 NATO ammo is a full-power rifle cartridge developed for military use and standardized by NATO during the 1950s. Known for its combination of power, range, and accuracy, the 7.62x51 NATO has served in battle rifles, machine guns, and precision rifles for decades.

Its widespread military adoption also helped establish a lasting presence in the civilian shooting community, where rifles chambered for the cartridge are commonly used for target shooting, competition, training, and recreational shooting.

The history of the 7.62x51 NATO cartridge can be traced to U.S. military ammunition development following World War II.

The U.S. military sought a more compact rifle cartridge capable of providing performance comparable to the 30-06 Springfield service cartridge while using a shorter case suitable for a new generation of rifles.

Experiments conducted at Frankford Arsenal during the 1940s led to the T65 series of developmental cartridges. Early work drew heavily from the proportions of the 300 Savage, while experimental cases were produced from shortened 30-06 cases.

The T65 design evolved through several versions until reaching a 51mm case length and the general configuration associated with today's 7.62x51 NATO cartridge.

Rather than being the invention of a single person, 7.62x51 NATO was the product of a U.S. military development program, with Frankford Arsenal playing a central role in developing and refining the T65 cartridge family.

At first glance, 308 Winchester and 7.62x51 NATO ammo appear almost identical.

The cartridges share the same basic case dimensions and are closely related historically, but they were developed for different markets and follow different ammunition and chamber standards.

The most important differences involve pressure specifications, chamber dimensions, headspace tolerances, and intended use.

The 308 Winchester was introduced commercially by Winchester in 1952. It was based on the experimental T65 cartridge developed during U.S. military efforts to create a shorter replacement for the 30-06 Springfield.

The military version evolved into the 7.62x51 NATO, which was standardized by NATO in 1954.

Because the two cartridges share such similar dimensions, the terms 308 Winchester and 7.62x51 NATO are sometimes used interchangeably. However, shooters should understand their differences before selecting ammunition for a particular rifle.

Although 308 Winchester and 7.62x51 NATO are closely related, they are not simply two names for the exact same cartridge specification.

Understanding their pressure standards, chamber tolerances, and intended applications can help shooters select appropriate ammunition while getting the performance their rifle was designed to provide.

SAAMI rates .308 Win at 62,000 psi. NATO rates 7.62x51 at 415 MPa, about 60,190 psi.

The two bodies use different test methods, so the numbers do not line up one to one. Zediker notes commercial .308 Win ammo is normally loaded to a higher pressure maximum than mil-spec NATO ammo.

Higher pressure in a longer chamber is the core concern. The case expands farther before the shoulder meets the chamber wall, and thinner commercial brass has less margin to stretch.

Headspace is the distance from the bolt face to the point where the case shoulder stops in the chamber.

Per Shooting Sports USA, the SAAMI .308 Win GO gauge measures 1.6300 inches and the NO-GO gauge measures 1.6340 inches. The 7.62 NATO minimum measures 1.6380 inches and the reject gauge measures 1.6455 inches.

A rifle at the long end of the NATO spec gives a .308 Win case over 0.010 inches of extra room compared to a SAAMI .308 NO-GO gauge. Zediker reports some commercial .308 ammo comes apart in a true NATO chamber.

Have a gunsmith check headspace on any surplus rifle before you fire commercial .308 Win in the gun.

Task & Purpose reports an average .308 Win case weighs 160 to 170 grains, while an average 7.62 NATO case weighs over 180 grains.

The extra brass sits inside the case, so interior volume drops to about 52.0 grains of water versus 56.0 grains for .308 Win, per GunUniversity.

If you reload, the smaller interior of military brass raises pressure with the same powder charge. Start with reduced loads when you work up with 7.62 NATO brass. Many military cases also use crimped primers, which need the crimp removed before you reprime.

GunUniversity compared Winchester USA Valor 149 grain 7.62x51 NATO against Federal American Eagle 150 grain .308 Win.

At the muzzle, the .308 load ran about 2,820 fps and 2,648 ft-lbs. The 7.62 NATO load ran about 2,790 fps and 2,575 ft-lbs. The gap is under 3 percent at the muzzle. At 500 yards, the NATO load held about 1,878 fps and 1,167 ft-lbs against 1,808 fps and 1,089 ft-lbs for the .308 load.

Bullet shape drives the reversal, not the cartridge. For hunting and range use, the two rounds deliver near-identical performance with comparable bullet weights.

Read the barrel stamp before you buy ammo. A rifle marked .308 Win fires .308 Win and 7.62x51 NATO.

A rifle marked 7.62x51 NATO fires 7.62x51 NATO, and the rifle maker decides whether commercial .308 Win is approved. Primary Arms flags older military rifles as the highest-risk group for commercial .308 Win.

Some rifles carry both markings or a hybrid chamber. If the markings or manual leave you in doubt, contact the manufacturer.

• Bulk range practice in a .308 Win rifle: 7.62x51 NATO M80-style 149 grain FMJ. Winchester USA M80 and Federal Lake City XM80 both fit this role.
• Deer and elk hunting: .308 Win soft point or bonded loads. FMJ does not expand reliably, and many states prohibit FMJ for big game. Check your state regulations.
• Precision and match shooting: .308 Win match loads with 168 or 175 grain boat-tail hollow points, or 7.62x51 M118LR-style 175 grain loads. A rifle stamped 7.62x51 NATO only: 7.62x51 NATO ammo. Fire commercial .308 Win only if the rifle maker approves and a gunsmith confirms headspace.

Bottom Line: Buy 7.62x51 NATO for bulk practice in any .308 Win rifle. Buy .308 Win for hunting and match work, and keep commercial .308 out of 7.62 NATO rifles unless the maker approves.

Safety Note: Always confirm the chamber marking on your barrel, wear eye and ear protection, and follow federal, state, and local laws for ammunition purchase and use.

Question: Is 7.62x51 NATO safe to fire in a .308 Win rifle?
Answer: Yes, in a rifle in good condition. GunUniversity, Primary Arms, and Shooting Sports USA all state 7.62x51 NATO fires safely in a .308 Win chamber. The NATO round runs at a lower rated pressure, and the tighter .308 chamber limits case stretch.

Question: Is .308 Win safe to fire in a 7.62x51 NATO rifle?
Answer: SAAMI does not list .308 Win in a 7.62 NATO chamber as an unsafe combination. GunUniversity still advises against the practice, and Primary Arms flags older military rifles as the main risk. The NATO chamber allows more headspace, and thinner commercial brass stretches more under higher pressure. Follow your rifle maker's guidance.

Question: Is 7.62x51 NATO weaker than .308 Win?
Answer: Only slightly at the muzzle. GunUniversity measured a 149 grain NATO load at about 2,790 fps and a 150 grain .308 load at about 2,820 fps, a gap of 30 fps. Bullet shape and weight matter more than the cartridge label.

Question: Why does 7.62x51 NATO brass weigh more than .308 brass?
Answer: Military cases use thicker walls. Task & Purpose reports average 7.62 NATO cases weigh over 180 grains versus 160 to 170 grains for .308 Win. The thicker walls reduce interior capacity to about 52 grains of water, per GunUniversity.

Question: Is M80 ball ammo good for hunting?
Answer: No. M80 uses a full metal jacket bullet built for military use and target practice, not controlled expansion. Many states ban FMJ for big game. Choose a .308 Win soft point or bonded hunting load.

Question: What are the different types of 308 ammo?
Answer: In today's market, owners can choose from a wide variety of 308 ammunition, ranging from the traditional full metal jacket (FMJ) to hollow points used for hunting. In addition, pointed soft-point (PSP) cartridges offer greater accuracy over longer distances, and specialty ammo like polymer-tipped is also available in 308. Lastly, most 308 Winchester ammo will have brass or steel casings that house the bullets and weigh between 100 and 200 grain.

Question: Does the military use 308 or 7.62x51 Ammo?
Answer: The US military does not use 308 Winchester ammunition. Instead, in 1954, the military adopted the 7.62x51 NATO, a cartridge that was developed from the 308 Win, but has significant differences. The civilian round is loaded to a higher pressure than the military round, and the parent case features a smaller headspace and thinner casing than the NATO cartridge.

• Shooting Sports USA (NRA), 7.62 NATO vs .308 Win
• Primary Arms, 7.62x51 vs 308, Does It Matter and What's the Difference?
• GunUniversity, 308 Winchester vs 7.62x51 NATO, Are They the Same?
• NSSF/SAAMI, Official Specifications

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