SSN Vet
Member
whats the difference?
the chamber geometry and the rated pressure.
5.56 chambers are cut looser (think full auto) and are rated for higher pressue.
The cartridge exterior geometry is identical. But military ammo is loaded to higher pressures.
from what I've read, many barrels with the .223 Rem stamp can handle the pressure....but how do you know for sure?
There is also a cross over chamber called the Wylde chamber that can handle either.
If your not shooting mil. surp. ammo. I don't think it's an issue.
You can certainly load Lake City brass with data from your loading manual and shoot it in a barrel stamped .223 Rem. However, you must work up your loads seperately from your .223 brass, as the case volume of the LC brass is slightly smaller.
Seems that these days, most ARs have either 5.56 or Wylde chambers.
.223 Rem is predominate on bolt action rifles, where nice tight chambers are desireable for accuracy reasons.