The dynamic between .223 Remington and 5.56 NATO is pretty well known; most rifle owners are aware that the former can be run in rifles chambered for the latter, but not vice versa. But the interaction between two other, similar rounds, 7.62x51mm NATO and .308 Winchester, is somewhat less understood, partially because it’s more complex.
In both cases, two distinct rounds share a developmental history that led them to be similar enough to be interchangeable in some cases, but different enough to be unsafe in others. Below, we’ll take a look at the similarities and differences between 7.62×51 and .308, and review when it is safe to use them in place of one another and when it is not.
What is 7.62×51?
Properly denoted as 7.62x51mm NATO, this cartridge was born shortly after the close of the Second World War. It was developed as an alternative to the larger, more powerful .30-06 Springfield, standardized by the nascent North Atlantic Treaty Organization, and fielded by the US Military in the M14 rifle.
Over the years, it would slowly be phased out as a general-purpose round and replaced in that role by 5.56x45mm NATO with the adoption of the M16. However, 7.62×51 still found use in a wide range of more specialized roles, primarily as a machine gun, DMR, and sniper cartridge–where it continues to be used today.
One of the reasons 7.62x51mm (Sometimes colloquially known as 7.62 NATO) was chosen from among the field of competitors to replace .30-06 Springfield is the similarity of the two cartridges’ ballistic profiles. .30-06 have served well in WW2 and was well-liked for its power and range, but was difficult to control in fully automatic fire, which would become a standard feature in the newly-adopted M14.
7.62 offered similar ballistics, but with less recoil and a shorter overall length, which was convenient for box-fed rifle designs. With comparable bullet weights, it offered slightly less muzzle velocity and shorter effective range, but was close enough that the benefits to recoil and controllability were seen to be worth the tradeoff.
7.62×51 is available in a variety of different loads, but only a handful are available to civilians. The most common is the ubiquitous 147-grain load, which was the typical ammunition used during the M14’s short tenure as the U.S.’s main battle rifle.
A popular variant is the M118LR load, which is a specialized cartridge used primarily for DMR and sniper applications. This load features a heavier 175-grain boat-rail hollow point bullet for greater wind resistance and long-range efficacy.
What is .308 Winchester?
Often, after developing new technologies for military applications, companies will attempt to maximize their return on investment by adapting their inventions for the civilian market. Such was the case with .308 Winchester.
While the 7.62x51mm cartridge was still in the experimental phase with NATO and military users, Winchester took what they had learned from their contribution to its development and created the .308 Winchester, which they brought to market in 1952–two years before NATO standardized the experimental 7.62 round as an official cartridge. As such, .308 Winchester is technically the older of the two, despite 7.62×51 having been developed first.
.308 Winchester rapidly surged in popularity as a hunting cartridge. Its ballistics, which are nearly identical to 7.62x51mm in comparable loadings, offered sufficient energy to ethically hunt most game in the lower 48 states. Unlike .30-06 Springfield, though, it fits in a short-action receiver, meaning rifles could be lighter and shorter. The round also lends itself well to a huge variety of different loads, ranging from 125gr bullets all the way to 210-grain projectiles.
Today, the .308 Winchester remains one of the most popular cartridges in America for hunting and is also commonly used in competition and other applications.
Key Differences Between 7.62×51 and .308 Winchester
Despite their similarities, there are a few things that set 7.62x51mm and .308 Winchester apart. Their case specifications are slightly different, as are their pressure ratings.
7.62x51mm is a NATO cartridge, with a maximum chamber pressure rating of 415 megapascals–that’s a tad over 60,000 PSI. .308 Winchester, on the other hand, is rated slightly higher, with a maximum SAAMI spec of 62,000 PSI. This means that, unlike the .223 Remington vs 5.56 NATO dynamic, in this case, the civilian version of the cartridge is actually the higher pressure of the two. However, the two are close enough that the maximum pressure difference is extremely unlikely to present an issue when used interchangeably.
Can You Shoot 7.62x51mm in a .308 Winchester Rifle?
However, this does not necessarily mean that it is always safe to shoot one cartridge in a rifle designed for the other. While it is generally safe to shoot 7.62×51 through a rifle chambered in .308 Winchester—though you should always defer to the manufacturer’s instructions when in doubt—the inverse is not always true.
Though both were based on the proto-7.62x51mm experimental cartridges that would eventually be standardized by NATO, the two cartridges diverged relatively early in the development process, before the specifications for either had been set in stone. Minor modifications were made to each as they were refined and improved prior to standardization, leading to small differences in case dimensions.
While things like case wall thickness have little impact on compatibility, the slightly different headspace requirements can be a concern in some cases. Due to this and the difference in chamber pressures, many consider .308 Winchester to be unsafe to fire in 7.62x51mm firearms, particularly older rifles that may not benefit from modern metallurgical advancements and may not have been designed with .308 Winchester in mind.
Because issues of compatibility arise primarily from variations in headspace and case design rather than pressure, though, 7.62×51 and .308 Winchester can both be used safely in any suppressor rated for .308 Winchester or larger calibers.
Ballistic Comparison
In most respects, 7.62x51mm and .308 Winchester are quite similar in ballistic profile when loaded with similar projectiles. .308 Winchester often displays marginally higher muzzle velocities and slightly less drop over distance due to its higher chamber pressure rating and slightly superior case capacity, but the delta between the two is small enough that this rarely makes a practical difference.
Usually, the ballistics of the two cartridges are similar enough that they can even utilize the same drop-compensation reticles, so if your scope reticle is designed for use with .308 Winchester, 7.62×51 ammunition should line up well enough to be functional for most applications.
Where the two start to significantly diverge is in the variety of loadings available. 7.62 NATO is only commonly available in two loads–the standard 147-grain and M118LR–.308 Winchester can be had in a myriad of different bullet weights and designs, loaded with dozens of different powders. This makes the latter much more versatile than the former.
.308 Winchester has also benefited from the slow progress of technology over the years. Because it is one of the most popular hunting rounds of all time, every advancement in bullet technology inevitably finds its way into .308 Winchester sooner rather than later, such as the heat-resistant polymer-tipped rounds utilized in Hornady’s ELD ammunition. 7.62×51, having been standardized decades ago, has seen relatively few changes.
AR-10 and Other 7.62/.308 Rifles
7.62x51mm and .308 Winchester are some of the most popular rounds of all time, used by military forces, hunters, competitors, and recreational marksmen alike for decades. Let’s take a look at some of the most common and iconic rifles.
AR-10
The AR-10 is arguably the most iconic rifle of this batch. Often thought of as a scaled-up AR-15 chambered in .308 Winchester (and many other cartridges), it’s actually an older design than the AR-15. The AR-10’s early success led to the development of the AR-15, which of course became one of the most popular rifles of all time. In fact, the two rifles are so similar that AR-10 and AR-15 parts are sometimes interchangeable.
For those curious about the distinction between the two firearms, we go into greater detail in our AR-15 vs AR-10 breakdown.
AR-10 rifles share nearly everything that makes AR-15s great. Simple operation, intuitive and ergonomic controls, and extremely user-friendly construction make it a very easy rifle to operate and work on. The aftermarket for the rifle is vast, allowing users almost limitless customization.
The AR-10 has even been used for military applications, albeit primarily in a DMR role rather than as a general-purpose battle rifle.
Paired with the best AR-10 scope for your application, an AR-10 makes an excellent platform for a wide range of uses. Whether you want a hunting rifle, long-range gun, or competition rig, you can build an AR-10 for the purpose.
SCAR 17
Made famous by its military pedigree, reputation for unmatched ruggedness, and pop culture popularity, the SCAR 17 is one of the best-known rifles chambered in 7.62×51.
The SCAR 17 features an innovative polymer lower receiver, allowing it to achieve a significantly lower overall weight than most other semi-automatic rifles of the same caliber. Its piston-driven operating system allows for easier tuning than direct impingement designs. Combined with an effective muzzle brake, it’s known to be one of the softer-shooting rifles on our list.
The internal recoil spring assembly allows it to utilize a folding stock, a feature AR-10s can rarely match without aftermarket upgrades. For a more thorough comparison of the two rifles, check our guide to the SCAR 17 vs. the AR-10.
HK G3/PTR/CETME
One of the original 7.62×51 battle rifles, the HK G3 and its imitators is a soft-shooting, though heavy, workhorse.
The primary draw of the design is the roller-delayed blowback action, which delivers smooth, soft recoil even during very rapid fire. The non-reciprocating charging handle is also an iconic element with its lock-back notch that allows it to be slapped downward to release.
While original HK G3 rifles are no longer made, the design spawned an entire industry of replicas that remain available from companies like Century Arms International and PTR.
Remington 700
When discussing one of the most popular hunting cartridges of all time, we would be remiss not to mention one of the most common hunting rifles. The Remington 700 is a bolt-action rifle that has been putting meat on tables all across America for decades and is a massively popular platform for the .308 Winchester.
However, its history does not end with hunting. The Remington 700 has been fielded in a variety of iterations by both police and military forces as a sniper rifle, including by the U.S. Army as the M24 and the Marines as the M40.
With an aftermarket that nearly rivals that of the AR-15, the Remington 700 is a perfect platform for everything from a custom long-range precision rig to a simple hunting rifle.
Conclusion
7.62x51mm NATO and .308 Winchester are more similar than they are different, but that doesn’t mean they are perfectly interchangeable. While firearms chambered in .308 Winchester can generally use 7.62×51 ammunition safely, the inverse is not always true.
Regardless, both cartridges have stood the test of time for a reason. Despite being nearly 70 years old, both remain highly effective, impressively versatile rounds that will continue to be strong choices for hunting, competition, and professional use for years to come.
