Not certain, but the MV you mentioned sounds a bit high. I think that 3200 would be more like it.
As for powder, with 55 gr. fmj bullets, you might try WC846. Do not offhand recall the loads, but this was a Winchester military surplus powder, used for 7.62mmNATO and the 5.56mm round, with 55 grain bullets. You might write to Winchester(Olin) at St. Marks, Florida, their powder plant is located there. They were heplful to me, some years back, and might still be.