The question of whether you can shoot .308 Winchester ammunition out of a 7.62x51 NATO chamber is a common one, and the short answer is generally yes, but with important caveats. While the two cartridges are very similar, there are subtle differences that can lead to significant problems if not carefully considered. This article will delve into the details, exploring the similarities and differences between the two calibers and the potential risks involved in mixing and matching.
Understanding the Calibers: .308 Winchester vs 7.62x51 NATO
Both .308 Winchester and 7.62x51 NATO are .30 caliber rifle cartridges, meaning the bullet diameter is approximately .30 inches (7.62mm). However, despite their similar names and dimensions, key distinctions exist:
Case Dimensions: A Subtle but Crucial Difference
The most significant difference lies in the case dimensions. While the overall length is nearly identical, the 7.62x51 NATO case is slightly larger in diameter and has a slightly different shoulder angle. This seemingly minor difference can have major consequences.
- 7.62x51 NATO: This military cartridge is designed for robustness and reliability under harsh conditions. Its slightly larger case dimensions contribute to its strength.
- .308 Winchester: This commercial cartridge prioritizes accuracy and consistency. Its dimensions are optimized for this purpose.
| Feature | .308 Winchester | 7.62x51 NATO |
|---|---|---|
| Caliber | .308 Winchester (7.62mm) | 7.62x51 NATO (7.62mm) |
| Case Length | Approximately 2.01 inches | Approximately 2.01 inches |
| Case Diameter | Slightly smaller | Slightly larger |
| Shoulder Angle | Slightly different | Slightly different |
| Pressure | Generally lower | Generally higher |
Pressure Differences: A Matter of Safety
The slightly larger case volume of the 7.62x51 NATO cartridge, combined with its design for use in military-grade firearms, often results in higher chamber pressures compared to the .308 Winchester. Firing .308 ammunition in a 7.62x51 chamber generally produces pressures within the safe range for both the cartridge and firearm.
However, shooting 7.62x51 ammunition in a .308 chamber can lead to dangerously high pressures, possibly resulting in:
- Chamber bursts: The firearm's chamber might fail catastrophically.
- Barrel damage: The increased pressure can cause bulging, cracking, or even complete separation of the barrel.
- Bolt failure: The bolt mechanism might fail, leading to injuries.
- Serious injury or death: This is the most severe potential consequence of exceeding safe pressure levels.
Why the Differences Matter: A Practical Perspective
The differences, while subtle, are critical for safety. The tighter chamber of a .308 rifle could lead to excessive pressures when firing 7.62x51 ammo, while the slightly looser chamber of a 7.62x51 rifle may allow safe firing of .308 ammo, although not always reliably.
Case Study: A Real-World Example of Failure
While not explicitly documented in a formal research paper, many firearms forums and online communities are rife with anecdotal evidence of firearm damage caused by improper cartridge usage. One forum post describes a user who experienced a cracked receiver after repeatedly firing .308 rounds in a 7.62x51 rifle. The high pressures and repeated cycles caused micro-fractures that eventually resulted in the firearm's failure. This highlights the risks involved and reinforces the importance of sticking to manufacturer's recommendations.
The Verdict: Proceed with Caution
The ability to shoot .308 Winchester out of a 7.62x51 chamber depends on several factors, including the specific firearm, ammunition characteristics, and the tolerances involved. However, it's crucial to consult the firearm's manual to determine whether it's safe to do so. Many firearms manufacturers explicitly state whether their rifle can safely chamber .308 in a 7.62x51 chamber, although they will likely recommend against doing so. Never attempt this unless you are absolutely certain of the risks and have confirmed the firearm's manufacturer recommendation. The potential consequences far outweigh any benefits.
Always prioritize safety and adhere to the manufacturer's specifications. Incorrect ammunition usage can cause serious injury or death.