Brass lots with different case capacities (H2O)

[buckhunter]

Pretty much had the same experience as dovehunter. Also found that normally by changing case's the pet load wasn't the pet load anymore. Sorry to say you will probably have to develope another pet load. I usually try to stay with the same manufacturer once a sweet spot is found.

[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

[Catfish]

Steve, Your test seem to be right on with what the wildcatters use as a rule of thumb. Your in crease in velocity will be 1/2 of the % of the increase in case volume. That assumes the same presure levels.