As far as the bullet diameter, yes. "223" and "Five-Five-Six" bullets all measure between 0.2238" and 0.2245" on the bearing surfaces. The can's bore is probably 0.275-0.300" or better...being a Surefire.
But I wouldn't do so until I called Surefire and asked them if they felt comfortable with the Valkyrie, and if so, at what barrel length minimum.
It's the PRESSURE rating that is key here, not the boolit.
-Nate