memes

And a .308 is a 7.62mm NATO. You can fire a 7.62 through a 308, but you shouldn't fire a .308 round through a 7.62 NATO gun because of a slightly different shell shape and higher pressure loads.

if there is one thing i will never put time into learning, it's all the variants of them.

While that's true, another reason not to put 5.56 into .223 is that 5.56 has a slightly longer casing that might not have room to expand in a .223 rifle.

This isn't true. Both 5.56 and .223 can be loaded to a variety of pressure specs. 5.56 being hotter is fudd lore due to it being the military spec.

The difference between the two comes down to how the neck of the cartridge is measured. The the 5.56 is rated to withstand a certain pressure...it does not mean it is always loaded to a higher pressure.

The reason you don't want to shoot 5.56 in a .223 is because the cartridge neck doesn't fit the chamber properly and the resulting incorrect headspace is what can cause a catastrophic failure ..again it's not due to the round being hotter.