Winchester 308 / 7.62 Ammo & Ammunition

Can I use 7.62 ammo in a 308?

Yes, you can fire standard 7.62 ammo in any currently produced rifle chambered for .308 Winchester. You need to understand beforehand the .308 'headspace' dimension spec. The .308 Winchester chamber headspace is between 1.630 and 1.6340 inches. While the dimensions of the 7.62x51mm, NATO is between 1.6355 and 1.6405 inches. This can be a problem with ammo companies in Europe that make ammo to NATO standards. Headspaces at 1.633" to 1.635" will be fine in a 7.62 NATO chamber. However, even that tiny difference is too significant for a .308 Win chamber. While it may seem that the size difference might not seem like a problem unless you fire the ammunition in a thinner brass in a long-chambered rifle. The brass will expand and could cause a dangerous rupture. The solution is to use a thicker brass chamber to handle the chamber's expansion. So it can be done, but you need to be aware of the type of 7.62 ammo you're using and the rifle you'll be firing.

What is the difference between 7.62 x51 and .308 Winchester?

There are two differences between the 7.62 x51 and .308 Winchester? The first is the internal differences and the barrel chamber length for the different cartridges. Thicker brass is better able to expand and accommodate these chamber variations. All-around, military brass is thicker than retail brass. This design feature accommodates NATO specifications and has varying chambers specs.

The case cartridges must withstand the rigors associated with automatic weapons. Because the 7.62 case cartridge has thicker walls yet has the same external dimension as the .308 case cartridge, the powder capacity of the 7.62 is lower than the .308. Consult their Reloader's Guide and adjust the powder loads according to the specific calibers of the rifles that will be fired from. It follows that other things being equal, the thicker case (smaller capacity) will generate higher pressure. Too high pressure may result in a primer leak and other pressure problems.

The most significant difference between the .308 Winchester cartridge and the 7.62 NATO cases is their specifically designed chambers. Typically, military rifles are made with slightly longer chambers (longer headspace). This ensures fast, easy feeding and ejection through rapid-fire sequences (i.e., auto-fire). The difference in this headspace between the two cartridge cases is approximately six thousandths of an inch, which may seem tiny, however, significant.

The .308 Winchester is specified for a 'hotter' powder load than the 7.62; the brass will expand, firing it in a chamber with the added headspace. With a thinner brass wall design, the results may lead to an over-expansion (i.e., case ruptures, etc.).