.id like to know why the calibers are so close together. the 223 and the 556..why have 2 cartridges that fire from the same rifle as they do
They are exactly the same cartridge
1959...
Fearing the confusion of so many "Triple Deuce" nomenclatures, the .222 Special is renamed the .223 Remington.
5.56 is NATO spec. .223 is Sami.
5.56 is loaded to slightly higher pressures then .223
Tom Servo said:Short story: the military wanted a high-velocity, smallbore cartridge. Armalite and Remington came out ahead in the race. It's actually a long and convoluted story. Daniel Watters has a detailed history here.
T. O'Heir said:"...the military wanted a high-velocity, smallbore cartridge..." No, they didn't. Nobody wanted either the M-16 or the .223/5.56(same thing before there was an internet. Common myth is that they are not exactly the same.).
A M-16/AR-15 was never intended to be a main battle rifle. It was designed to be an air crew survival weapon, period.
The U.S. military was ordered to adopt 'em by Robert McNamara because he thought he(being a FORD executive) knew more about what was required than the military leaders.
Then the rest of NATO was told adopt it or the U.S. would pull out of NATO. Just like they were when the 7.62 was adopted ten years earlier.
Learned something new today. I thought I had researched it enough to to think I found the correct answer. I wish I could remember the long article ( from a respected source iirc )I read that kept referring to the pressure differences.Common misunderstanding. NATO spec is P.S.I. SAAMI spec is C.U.P. The spec for 223 is 52,000 C.U.P. and 62,000 P.S.I. the same as 5.56 P.S.I. spec. Just a different measurement scale used for standard.
Also 556 has less case capacity than a SAMMI spec 223. The 556 has thicker case wall near the head to prevent case head separation especially during full auto fire.
The Army, getting its orders, selected a set of performance criteria which the .222 simply could not meet.