.308 vs 7.62×51 (NATO): Are They Interchangeable?

I often come across questions about the compatibility of .308 Winchester and 7.62×51 NATO cartridges. Are .308 and 7.62×51 interchangeable? Yes, with caution. If your rifle is chambered in .308 Winchester, you can shoot both rounds, but you should avoid frequent use of 7.62 NATO. The reverse must not be tried due to potential pressure and chamber differences.

I understand the curiosity and confusion that often surround these two rounds. So today, I’ll gradually peel back the layers of information with the basic question: Are .308 Winchester and 7.62×51 NATO truly interchangeable?

Join me in the historical evolution, technical intricacies, and practical considerations that define the relationship between these powerful cartridges.

Are .308 (Winchester) and 7.62×51 (NATO) Interchangeable?

The journey begins with the development of 7.62 NATO, born out of the military’s desire to mimic the .30–06 M2. Winchester (which is impressed by the round) brought it to the civilian market as a .308 Winchester.

The external dimensions of the cases are the same, and the 7.62 NATO was actually developed from the .308. The .308 Winchester and 7.62x51mm NATO rounds are quite similar, but they are not entirely interchangeable. However, they are only one-way compatible.

• If your rifle is chambered in .308 Winchester, you can safely fire both .308 Winchester and 7.62x51mm NATO in it.
• On the other hand, if your rifle is chambered in 7.62x51mm NATO, you should stick with 7.62x51mm NATO ammunition.

While you can fire 7.62 in a rifle chambered for .308, you must not use a .308 Winchester in a rifle chambered for 7.62x51mm NATO regularly.

.308 WINCHESTER VS 7.62×51 NATO: Are They Same?

The .308 Winchester and 7.62x51mm NATO may seem similar, but they are not identical.

.308 Winchester and 7.62x51mm NATO reveal their distinctions in brass thickness, chamber design, and internal pressures. These distinctions make them only one-way compatible as you’ve already known from the above.

.308 vs 7.62×51: What Are The Differences?

1. Brass Thickness

• The 7.62 NATO has thicker walls due to military specifications, accommodating various chamber specs and enduring automatic weapon stresses.
• Thicker brass in 7.62 reduces powder capacity compared to .308, leading to lower pressure. So, reloaders need to adjust powder loads accordingly.

2. Barrel Chamber Length

• Military rifles typically have slightly longer chambers (headspace) for fast feeding and ejection during rapid-fire sequences.
• The published headspace difference is approximately 6,000th of an inch which impacts how each cartridge stretches upon firing.

3. Pressure Differences

• Firing .308 in 7.62 chamber risks over-stretching due to pressure disparities.
• .308 Winchester operates at a higher pressure (62,000psi) compared to 7.62x51mm NATO (60,191psi). 

4. Compatibility

• Rifles chambered for .308 can safely shoot both .308 Winchester and 7.62 NATO.
• Rifles marked for 7.62 NATO should only use 7.62 NATO rounds to avoid potential issues associated with pressure and chamber differences.

Pro Tips:

• While .308 Winchester-chambered rifles can handle 7.62 NATO occasionally, frequent use is not recommended.
• Always follow manufacturer recommendations and consult for a list of Generally Accepted Firearms and Ammunition Interchangeability.

.308 WINCHESTER and 7.62×51 NATO Ballistics Comparison

When we talk about the .308 Winchester and 7.62×51 NATO, it’s like comparing siblings—similar, but with their unique traits. Let’s break down their differences in a way that’s easy to understand.

What’s the Main Catch Here?

Though these cartridges may seem similar, differences in case capacity and max pressure highlight distinct ballistic characteristics.

• Bullet Diameter: Both cartridges share a 0.308-inch bullet diameter. They both fire a bullet of the same size—0.308 inches.
• Case Capacity: .308 Winchester has a bit more room inside with 56.0 gr H20 compared to 52.0 gr H20 in 7.62×51 NATO.
• Max Pressure: .308 Winchester plays it a bit tougher with a max pressure of 62,000 PSI, while 7.62×51 NATO operates at 60,181 PSI.

Is a 7.62×54 the Same as a 7.62×51 NATO and .308?

The 7.62x54R stands out as a rimmed Russian cartridge. It is used in rifles like the Mosin-Nagant. Unlike the .308 and 7.62×51 NATO, it boasts a rimmed design and a larger .311 bullet diameter that aligns more with the .30/06 in terms of power.

Conversely, the .308 Winchester and 7.62×51 NATO share a closer relationship. While gun experimentalist interchanges them due to their similarities, they need to take precautions.

The .308 (known for higher pressure) is not suitable for all 7.62 NATO chambers. Despite similarities in energy levels and historical applications, you should not swap 7.62x54R with .308 or vice versa.

Now, the real talk—swapping the Russian cousin with the pals? Not a great idea. They’re like siblings with different shapes and sizes. Because the rounds differ significantly in length, shape, and bullet specifics, they pose risks from gun damage to catastrophic failure.

.308 vs 7.62×51: Sum it Up

The key takeaway is that Though .308 and 7.62×51 may seem like siblings, there are some differences in pressure specifications, ballistics, and historical evolution.

So, next time you load up your rifle, do so with a keen eye on the details for a safe and enjoyable shooting experience. It’s like having a favorite recipe – you want to stick to the ingredients that work best for your specific kitchen!