Dimensions are NOT the same, the Hornady is larger at the shoulder and shorter body length. You could run the Hornady case in a 17 Ackley F.L.die but will end up slightly shorter and you will still have to fireform. Just take a deep breath and make the Ackley from hornet brass, and you will be better off. The other option would be to set the barrel back a thread or two and rechamber to the Hornady. In my opinion, not a practical solution.  Others on this forum may chime in!