When you say “308”, I’m assuming you’re talking about the cartridge called .308 Winchester.

It’s easier to start with the similarities. Both chamber a bullet of .308″ diameter; that’s where it begins and ends.

The 30–30 started out in 1895 being called the .30 Winchester Smokeless; when adopted by other manufacturers, it was renamed to something more generic to avoid using the Winchester brand name. It’s a moderately powerful cartridge with a rimmed case that works well in lever action rifles. The bullets are almost always round or flat nosed because they were intended to be loaded in a tubular magazine. A spire-point bullet could strike the primer of the round ahead of it during recoil, setting off a catastrophic detonation in the magazine. Typical velocity from a 150-grain flat nose bullet is 2,390 ft/s, for 1,903 ft of energy. It’s probably the most popular deer hunting cartridge in North America.

The .308 Winchester came to us in 1952 as the civilian version of the 7.62x51mm which was adopted by NATO in 1954. Winchester, like the military, saw the advantage of a cartridge with close to the same power as the 30–06 in a shorter case. The case is rimless as it was designed to work in a semi-auto action and it uses a modern pointed bullet because the rifles chambered for it would use box magazines. Being designed for higher pressures (because nothing chambered for it could have been made in the 19th century) typical velocity with a 150 grain bullet is 2,820 ft/s, with 2,648 ft⋅lb energy. It also works extremely well in bolt action rifles.

Now you know!