[Freddymac]

I got some .223 ammo from my fathers friend the other day. I noticed while shooting in that it seemed to be loaded really hot. So it got me thinking, this might really old stuff. Its head stamp is: 5.56 80.11 P S

If any one has any info about these rounds I would be greatly appreciative.
Thanks
Fred

[Hawkman]

If you are shooting a rifle chambered for .223 Remington, then that is the reason that the 5.56 seems hot. The .223 chamber has shorter leade (the lands and grooves of rifling begin closer to the chamber) than a 5.56 chamber. With a 5.56 military round crammed in, you are getting a pretty good pressure spike as the powder ignites.

A 5.56 will easily shoot .223, but not necessarily the other way around.

[Freddymac]

It’s an XM15 chambered for 5.56. I’m sorry I always say .223, I’m not fond of saying metric dimensions. I am aware of the difference in loading between .223 and 5.56. The 5.56 is a military round and is loaded hotter, but these were showing minor signs of high case pressure. I’m not sure of the terminology, but there is a spot on the back of the case that looks sheared. I’ve seen this before in a magazine in an article about reloading

[EddieCoyle]

Look here:

http://cartridgecollectors.org/headstampcodes.htm

[Freddymac]

I'm at work and the stupid computers won’t let me on that website. Thanks for the help though.

[jonnyc]

It is 1980 South Korean military surplus.

[Freddymac]

Thanks a million.

[ny32182]

I was under the impression that the external dimensions of 5.56 and .223 cartridges were identical, but it was the lower pressure spec of .223 that made it not always OK to shoot 5.56 loads in a .223 chamber.

Whereas in the .308/x51 world it is reversed: Common wisdom there goes that x51 can be fired from a .308 chamber, but .308 can't always be fired from a x51 chamber, as the .308 is speced to a higher pressure level. That is, according to info on FALfiles.

[Freddymac]

Thats right, you can shoot .223 in a 5.56, but you should not shot 5.56 in a .223 even though they have the same dimensions. i'm not sure about the 308 vs 7.62.