I knew the 3-1/4" was nitro loaded. What I meant was that it really fell out after Jeffery introduced the 3".
There are good reasons to use the 3" case, one being the thicker rim. The "Tropical" load of 55grs of cordite was introduced in the 3-1/4" case due to extraction problems which can be made worse with a thin rim.
I think the OP is about modern made guns. There really is no reason to use the 3-1/4" case today.