I don't know much about the ARC, but my LC 5.56 brass will usually be around 30.6 grains capacity. AI-ing the case would put it around 32 grains, fwiw.From my understanding, the 22 ARC has 4 to 5 grains greater case capacity at 34 grains vs 29 to 30 depending on what brand case the 223AI is made from. Not arguing, just curious since using those numbers the 22 ARC has 13 to 15 percent more case capacity.
Jay
I guess even a bit more than that according to the chart @wind gypsy posted.