Ak Guy
Member
I just read an article in Guns Mag about not shooting 5.56 NATO in .223 chambers. My AR is marked as "5.56 mm" , but is that the same as "5.56 NATO" ?
While this is true there are still manufacturers cutting chambers to the true .223 Spec, and now ammo like Black Hills 5.56 77gr OTM - AKA Mk262 Mod 1 - is fairly available. Mk 262 and similar 5.56 loads are running on the hot side pressure wise in 5.56 chambers. I'd not want to shoot it in a .223 Rem chamber with the shorter leade and resultant pressure spike.There are minor dimensional differences between .223 Rem and 5.56 NATO, but generally not enough to create issues.
Most rifle manufacturers today recognize that their .223 chambers will likely seen 5.56 NATO rounds at some point and allow for the difference in their chamber cuts.
^^^ This.Yes. Before there was an Internet, the .223 Rem and 5.56 NATO were the same thing. Ditto for .308 Win and 7.62 NATO. Millions of rounds of surplus ammo(there was lots of it long ago), in both chamberings, got fired out of rifles, both milsurp and civilian, with no fuss.