Thanks much for the inpu, Gentlemen. I appreciate you sharing your expertise. Think I will nibble around, 43 and 43.5, the bolt lift at 46 was pretty stiff and 3150 seems likke a pretty optimistic MV for a Roberts.
Tried earlier with 43gr of IMR4350 with different OALs. None were particularly good but 2.75" was the best.. So perhaps 43gr and 45.5gr at that OAL.

115gr PTs at just under 3000fps sounds like a real sweet spot for my needs.

Thanks again (wish I had some Ramshot Magnum!