A bit of gun stuff to help keep you on the straight and narrow when watching the news, reading the paper etc.
The 5.56 (223 Remington when in a hunting rifle) and the cartridge for the M16 and similar rifles, will be described in various terms such as high calibre, extremely powerful, the extremely high velocity and whatever else you want to add.
Now for the reality. Of centre fire rifles (as opposed to the rim fires) it is the least powerful of the commonly available cartridges. Of the smaller bore size cartridges it has the lowest velocity of the commonly available cartridges.
The AK47 cartridge, the 7.62 X 39, same bullet diameter as the old 303 but much lighter in weight and slower. It the 30 calibre range it is the lowest powered that is commonly available, even less than the lever action 30/30.
The 7.62 NATO replaced the 303 and 30/06. It is about the same power (kinetic energy) as the 303 but with a lighter bullet going a bit faster. 303 Mark VII ammo was 174 grain bullet at 2440 f/s the 7.62 NATA is generally a 150 grain bullet at 2750 f/s. On the power scale of sporting cartridges it is very low level.
These days the 7.62 NATO is used only in machine guns and also in the shorter range sniper rifles, which is most sniper rifles.
A sporting cartridge like the 30/378 Weatherby uses the same diameter bullets as the 7.62 NATO but has 2.5 times the powder. Something like the 30 or 338 Chey Tac use 3 time plus more powder. Of course there is a price to pay with short barrel life, very savage recoil and extreme muzzle blast. These sort of rifles are almost always used with a muzzle brake to control recoil and that makes ear muffs (often with ear plugs) mandatory.