[sandman]

Collecting data to answer my own question (though i do appreciate everyone's input so far). Pet load in question is Nosler 120gr BT in front of 49.0 gr of Win760, Fed 215 primer to a COL of 2.850.

Federal Nickel (old case): 53.5gr capacity, avg vel 2924, group 0.44" (4 shots)
Hornady (new case): 55.5gr capacity, avg vel 2868, group 0.51" (4 shots)

So, a 3.74% increase in case capacity results in a 1.91% decrease in velocity (essentially a 2:1 ratio). Does this relationship generally hold true for changes in case capacity?

As for the new pet load, I may just leave well enough alone. The decrease in velocity really makes little difference in trajectory, especially hunting normal distances in Pennsylvania woods. I'll probably still load a few at 49.5, 50.0, 50.5, and 51.0 to test--plenty of time on my hands now that the season is over. Plus, it gives me an excuse to shoot more.

--
Steve