While externally similar, the main difference between the 7.62×51 NATO and the .308 Winchester are that the .308 operates at a higher pressure, up to 62,000 psi with tighter chamber tolerances, while the 7.62×51 is a military round with thicker brass, lower pressure, 50,000 to 58,000 psi and a longer, looser headspace.  Generally, it is safe to fire 7.62×51 in a .308 rifle but firing a .308 in a 7.62 rifle is generally not recommended due to higher pressure.

Key Differences

Pressure:  .308 Winchester is loaded to higher pressures, whereas the 7.62 NATO operates at slightly lower, more consistent pressures.

Chambering:  The 7.62×51 chambers are usually longer to ensure reliability in automatic weapons.

Brass Thickness:  7.62 cases often have thicker walls and less internal volume compared to .308, which can lead to higher pressures if using .308 reloading data.

Performance:  .308 Winchester is often considered to have better terminal velocity and accuracy, while 7.62 is designed for reliability in combat environments.

Interchangeability Guidelines:  7.62 in .308 rifle is generally safe.  The tighter chamber of the .308 rifle will handle the slightly smaller 7.62 cartridge.

.308 in a 7.62 rifle, generally not recommended.  The higher pressure of the .308 can cause issues in older or looser-tolerance 7.62 rifles.

ALWAYS CONSULT THE FIREARM MANUFACTURER’S GUIDELINES FOR SPECIFIC SAFETY AND COMPATIBILITY INFORMATION.

Be Safe Out There