.223 and 5.56 are a little different, but it’s mostly in case capacity and o/a cartridge length. Once can be higher pressure than the other, but I can’t recall which without consulting one of my reloading manuals. In almost all situations, they’re interchangeable. You can get into some other differences with o/a length when you’re talking about hand loading for bolt-action v. semi-auto, but that’s more of a specialty difference rather than a general purpose difference.
FWIW, the AR-10 came first, because Eugene Stoner was trying to directly compete with the M-14. It really didn’t go anywhere at the time, and it’s only become somewhat popular in the last 20 years or so. And it’s still not popular because 7.62x51mm is significantly more expensive to shoot than 5.56. But a 6.5CM AR-10 can be incredibly accurate to a very long range; it makes a great longer range hunting rifle.
It’s all good.
.223 and 5.56 are a little different, but it’s mostly in case capacity and o/a cartridge length. Once can be higher pressure than the other, but I can’t recall which without consulting one of my reloading manuals. In almost all situations, they’re interchangeable. You can get into some other differences with o/a length when you’re talking about hand loading for bolt-action v. semi-auto, but that’s more of a specialty difference rather than a general purpose difference.
FWIW, the AR-10 came first, because Eugene Stoner was trying to directly compete with the M-14. It really didn’t go anywhere at the time, and it’s only become somewhat popular in the last 20 years or so. And it’s still not popular because 7.62x51mm is significantly more expensive to shoot than 5.56. But a 6.5CM AR-10 can be incredibly accurate to a very long range; it makes a great longer range hunting rifle.