Understanding the Ammunition: .308 Winchester and 7.62x39mm
The .308 Winchester: A Legacy of Performance
The .308 Winchester, also known as 7.62x51mm NATO (though there are slight differences), is a ubiquitous cartridge in the world of shooting. Born from military development, it has become a favorite for hunters, sport shooters, and even law enforcement agencies. Its popularity stems from a combination of factors: its inherent accuracy, relatively flat trajectory, and considerable power. The .308 Winchester traces its lineage to the need for a shorter, more efficient replacement for the .30-06 Springfield cartridge.
This cartridge is typically chambered in bolt-action rifles, semi-automatic rifles, and some lever-action models. Its bullet diameter, a critical aspect for our discussion, is generally .308 inches. This diameter allows for optimal engagement with the rifling within the barrel, contributing to both accuracy and stability in flight. Ammunition manufacturers offer a vast array of .308 Winchester loads, from lightweight bullets designed for varmint hunting to heavier projectiles suited for larger game like deer and elk. The .308’s flat trajectory makes it well-suited for longer-range shooting, making it a popular choice for target shooters seeking to test their skills at considerable distances. The power of the .308 also makes it suitable for a wide variety of hunting situations, from open fields to dense forests.
The 7.62x39mm: The Workhorse of Eastern Bloc Heritage
The 7.62x39mm cartridge tells a different story, steeped in military history and the legacy of the Soviet Union. Primarily designed for the legendary AK-47 assault rifle, this round played a pivotal role in shaping modern warfare and continues to see widespread use across the globe. Unlike the .308’s origins in civilian development, the 7.62x39mm emerged as a military necessity, designed to provide effective firepower at relatively short to medium ranges.
The 7.62x39mm is commonly chambered in rifles like the AK-47 and its numerous variants, as well as in SKS rifles and some bolt-action designs. Its bullet diameter is slightly larger than the .308, typically ranging from .310 to .311 inches. The 7.62x39mm is prized for its reliability and its ability to function effectively in challenging conditions, a hallmark of its military design. While not achieving the long-range capabilities of the .308, the 7.62x39mm delivers substantial stopping power at moderate distances, making it effective for hunting medium-sized game in many parts of the world. Its versatility and availability continue to make it a popular cartridge among hunters and shooters alike.
The Risks of Mismatching Cartridges: A Recipe for Disaster
The Diameter Difference: A Critical Discrepancy
One of the fundamental differences between the two cartridges lies in their bullet diameters. While seemingly slight, the dimensional difference between a .308-inch bullet and a 7.62x39mm bullet (typically .310 to .311 inches) is a significant factor. When a bullet is fired, the barrel’s rifling engages with the projectile to impart spin, stabilizing it for flight. This process relies on a tight fit.
In a .308 barrel, the .308-inch bullet makes a good seal. The bullet is effectively gripped by the rifling, allowing the expanding gases from the burning propellant to push it down the barrel. However, when you try to fire a 7.62x39mm bullet through a .308 barrel, the larger bullet will be forced into a space that is not large enough. This can lead to a number of serious problems. The bullet might not seat properly at all. The bullet may deform under the excessive pressure. The bullet may get stuck in the barrel, also known as a squib load, and will likely render the gun useless. The expansion of gas is compromised. The bullet might be forced down the barrel, but the lack of a proper gas seal means that the expanding gases will leak around the bullet.
Chamber Pressure and Potential for Catastrophe
Beyond bullet diameter, the chamber dimensions and pressures associated with each cartridge pose another critical concern. The .308 Winchester chamber is designed to handle significantly higher pressures than the 7.62x39mm chamber. When a 7.62x39mm cartridge is used in a .308 rifle, the shorter cartridge case may not seat correctly in the longer .308 chamber. This can lead to a variety of issues, with potentially explosive results.
The most alarming is that the cartridge case might rupture. The pressure from the expanding gases will have nowhere to go but outwards. This can cause the barrel to bulge, crack, or even explode. Such a catastrophic failure can send fragments of the firearm in all directions, posing a significant risk of injury to the shooter and anyone nearby. Moreover, if the chamber is improperly formed, the breach can also become damaged or cracked, and the user may not be able to load a subsequent round.
The Risk of a Misfire
Even if the bullet manages to be pushed from the barrel, there is the potential for other complications. Misalignment can lead to a misfire. If the firing pin strikes the primer of the 7.62x39mm cartridge, and if the cartridge is not adequately seated, there is a risk that the primer will not ignite properly, or not at all. In a worst-case scenario, the cartridge could misfire, meaning the bullet does not leave the barrel. The gun may also become rendered useless, and will have to be properly serviced by a gunsmith.
Consequences, Precautions, and Safety: Staying Safe
Immediate Risks of a Mix-Up
The immediate risks associated with shooting a 7.62x39mm round out of a .308 rifle are very serious. Barrel damage can range from minor bulges to complete ruptures. Even if a barrel doesn’t immediately explode, the excessive stress can weaken the metal, making it more prone to failure in subsequent shots.
More gravely, there is the very real possibility of injury to the shooter. Shrapnel from a ruptured barrel can cause severe cuts, lacerations, and even penetrate the skin. The force of an explosion can also cause blunt-force trauma, leading to broken bones or internal injuries. Additionally, the shooter is at significant risk of hearing damage and eye injuries. Bystanders may also be hurt.
Embracing Responsible Firearm Practices
Prioritizing safety is paramount. There is no margin for error when it comes to firearms safety.
- Always carefully examine the ammunition before loading it into your firearm.
- Take your time to verify the cartridge’s markings and ensure they match the firearm’s caliber.
- Develop a habit of visually inspecting your ammunition and the firearm before each use.
- Read your firearm’s manual. This provides critical information, including which types of ammunition are and are not compatible with your firearm.
Dealing with Suspected Problems
If you suspect that you’ve loaded the wrong ammunition or experienced a malfunction, immediately cease firing. Do not attempt to disassemble the firearm yourself unless you are a trained gunsmith. Carefully unload the firearm, and seek professional help.
Moving Forward: A Final Word
Shooting 7.62x39mm ammunition in a .308 rifle is not only a mistake; it is a dangerous and potentially deadly act. The dimensional differences between the cartridges, coupled with pressure discrepancies, make this a recipe for disaster. Understanding the specific characteristics of your ammunition and firearm is essential for safe handling.
If you are in any doubt about the compatibility of ammunition with your firearm, err on the side of caution. Do not guess, and do not take risks. Invest time in learning about firearm safety, and seek training from certified instructors.
Remember, responsible gun ownership is a lifelong commitment to safety, education, and respect for the power of firearms. Stay informed, stay safe, and stay vigilant.
