If you use JB's 4:1 rule, if the ackley gains 4% in capacity velocity should rise by 1%, which at a nominal 3000 fps for the .223 makes for a 30 fps bump.

I've generally looked at ackleys as good for a 50 fps bump, anything beyond that is achieved by running higher pressures. With modern brass you can run 70,000 psi and not see pressure signs. So if the .223 is a 62 kpsi round, and published data is at 62 kpsi, the speed increase from the ackley is mostly achieved from running higher pressure, not from the increase in capacity.

But, one thing to consider is an action that can handle a belted mag case running 65 kpsi is going to be under much less strain running the petite .223 case at 70 kpsi.