Ruger M77 Mark II 223
I thought I new the answer to this question, after reading several articles I am confused. Can I shot 223 and 5.56 out of my Ruger M77 Mark II rifle? THE BARREL IS STAMPED 223.
My feelings are yes.
Originally Posted by bigfisherman
The case dimensions are externally identical. I say external because military brass is generally thicker and therefor equal powder charges will produce different pressure and velocities.
I don't think there would be a 5.56X45mm round out there would cycle an AR style rifle that would cause any problems for your bolt rifle.
The opposite is not true. There are several powder bullet COL combinations that will fire in your M77 that won't load or cycle the AR-15.