Originally Posted by 303tom
There is NO difference between the .223 Rem. & the 5.56 NATO !...................
Yep. I used to believe that, too.
Identical ammunition, in this case Lake City M855 from the same lot.
Here was my personal and unintentional experiment with 5.56 out of a .223. The rounds on the left were fired from a .223 chambered AR15. It consistently blew the primers. The rounds on the right were fired from a 5.56 chambered AR15. Same day, same ammo, two different chambers. .223 ammunition functioned without issue through both rifles.
Remedy: Ream the .223 chamber.
I have never had this issue with any Savage chambered in .223 (I've owned 3), or any other bolt gun I've owned with the exception of a .223 Weathery which exhibited indications of over-pressure when shooting 5.56.
For a synopsis and commentary of the SAAMI Bulletin "Unsafe Arms and Ammunition Combinations Technical Data Sheet" (1/1979, revised and updated Summer 2007), see: