The question of whether you can shoot 7.62x51 NATO ammunition out of a barrel chambered in .308 Winchester is a common one among shooters, and the short answer is nuanced: generally yes, but with caveats. While both cartridges use the same diameter bullet (.308 inch), subtle differences in their design can lead to issues if precautions aren't taken. This article will delve into the specifics of these differences, the risks involved, and best practices for safe and responsible shooting.
Understanding the Cartridge Differences: 7.62x51 vs .308 Winchester
Although often used interchangeably, 7.62x51 NATO and .308 Winchester are distinct cartridges with minor yet significant variations:
-
Case Dimensions: While the bullet diameter is the same, the 7.62x51 NATO case is slightly longer and has a larger maximum case volume. This difference in case dimensions is the root of most compatibility concerns.
-
Chamber Specifications: .308 Winchester chambers are typically designed to tighter tolerances than 7.62x51 NATO chambers. This is to ensure consistent headspace and reliable feeding. Firing a 7.62x51 round in a .308 chamber can potentially lead to dangerously high chamber pressure.
-
Pressure Levels: 7.62x51 NATO ammunition is loaded to higher pressures than .308 Winchester ammunition. This increased pressure, combined with a tighter .308 chamber, increases the risk of overpressure and potential catastrophic failure of the firearm.
-
Case Head Dimensions: 7.62x51 cases are slightly wider in the case head. This can lead to issues with extraction or even damage to the firearm.
Table 1: Key Differences between 7.62x51 and .308 Winchester
| Feature | 7.62x51 NATO | .308 Winchester |
|---|---|---|
| Case Length | Longer | Shorter |
| Max Case Volume | Larger | Smaller |
| Chamber Tolerance | Generally more lenient | Generally tighter |
| Pressure | Higher (SAAMI specification) | Lower (SAAMI specification) |
| Case Head | Slightly Wider | Slightly Narrower |
The Risks of Firing 7.62x51 in a .308 Barrel
The potential consequences of ignoring the subtle differences between these two cartridges can be severe:
-
Increased Chamber Pressure: The most significant risk is the potential for dangerously high chamber pressure. This can lead to:
- Bullet bulge or rupture: The bullet may deform or break within the barrel.
- Barrel burst: The barrel can split or break under excessive pressure.
- Receiver damage: The receiver can be damaged, potentially causing catastrophic firearm failure.
- Injury or death to the shooter or bystanders: This is the most serious potential outcome.
-
Failure to Extract: The slightly wider case head of the 7.62x51 round can cause difficulty extracting the spent cartridge from the chamber, possibly requiring disassembly of the firearm.
-
Damage to the Firing Pin: The increased pressure might damage the firing pin or other internal components of the firearm.
When it Might "Work": The Nuances of Compatibility
While generally discouraged, some sources suggest that firing 7.62x51 out of a .308 chamber might be possible without catastrophic failure under specific, tightly controlled circumstances:
-
Manufacturer's Statements: Some firearms manufacturers have stated their rifles can handle 7.62x51. However, this should never be taken as a blanket endorsement. Always check the manufacturer's specific documentation for your model of firearm.
-
Well-worn barrels: In a very well-worn .308 barrel, the slightly larger 7.62x51 may be more compatible. However, the risk of higher pressure remains substantial.
Important Note: Even with a well-worn barrel, the risk of catastrophic failure remains substantial. This is not a recommended practice.
Best Practices: Safety First
The safest and most responsible approach is to never shoot 7.62x51 ammunition in a firearm chambered for .308 Winchester unless explicitly stated and guaranteed by the manufacturer. This means carefully checking your firearm's manual and adhering strictly to the manufacturer's recommendations. Using the correct ammunition is crucial for the safety and longevity of your firearm, and, most importantly, your own well-being and that of others.
Using the wrong ammunition can result in significant injury or death. If you are unsure about the compatibility of your ammunition and firearm, seek the advice of a qualified firearms professional.
Conclusion: Avoid the Risk
The potential dangers of firing 7.62x51 NATO ammunition in a .308 Winchester chamber significantly outweigh any perceived benefit. Sticking to the manufacturer's recommendations and using the correct ammunition is the only safe course of action. Prioritizing safety is paramount when handling firearms. Always practice responsible gun ownership.