The .308 Winchester and 7.62x51mm NATO cartridges are often confused, and for good reason: they're remarkably similar. Both are .30 caliber rifle rounds, meaning the bullet diameter is approximately .30 inches (7.62mm). However, despite their similarities, there are key differences that affect their performance and applications.
Cartridge Dimensions and Pressure: Subtle but Significant Variations
The most crucial difference lies in their cartridge dimensions and maximum chamber pressure. While the bullet diameter is nearly identical, the 7.62x51mm NATO case is slightly longer and wider than the .308 Winchester case. This seemingly small difference results in a higher maximum average pressure for the 7.62x51mm NATO round.
This higher pressure allows the 7.62x51mm NATO to achieve slightly higher velocities with heavier bullets. However, it also means that .308 Winchester ammunition should never be fired from a rifle chambered for 7.62x51mm NATO. The higher pressure could cause catastrophic damage to the firearm. Conversely, while some 7.62x51mm NATO ammunition might fire safely in a .308 Winchester rifle, it's extremely risky and strongly discouraged due to the potential for overpressure. The .308 Winchester chamber is not designed to handle the higher pressure of the NATO round.
In short: Never use .308 Winchester ammo in a 7.62x51mm NATO rifle, but firing 7.62x51mm ammo in a .308 Winchester rifle is equally unsafe, even if it seems to function.
Ballistics and Applications: Similar, But Not Identical
Despite the pressure differences, the ballistic performance of the two cartridges is largely overlapping. Both are effective at medium to long ranges, suitable for hunting medium-sized game and military applications. However, the higher pressure of the 7.62x51mm NATO generally translates to a slight edge in velocity and energy at longer ranges.
The choice between the two often comes down to application. The 7.62x51mm NATO is the standard cartridge for many military rifles and machine guns, while the .308 Winchester is widely popular among civilian shooters for hunting, target shooting, and long-range precision shooting. This difference in prevalence largely stems from the different manufacturing specifications and tolerances intended for military and civilian use.
Ammunition Availability and Cost: A Factor to Consider
Both .308 Winchester and 7.62x51mm NATO ammunition are widely available, but the cost can vary depending on the manufacturer, bullet type, and current market conditions. Generally, .308 Winchester ammunition might be slightly more readily available and potentially less expensive in some markets, though this can fluctuate.
Conclusion: Know Your Cartridge
The key takeaway is this: While .308 Winchester and 7.62x51mm NATO cartridges share similarities, they are not interchangeable. Understanding the subtle yet critical differences in chamber pressure and dimensions is crucial for safe and responsible firearm handling. Always confirm the specific cartridge your firearm is chambered for before loading and firing. Failure to do so could result in serious injury or damage to the firearm.
