Daryl-

Talking about leaving black powder fouling in one's rifle is a definite taboo. In the wrong context or without proper preparation it's a recipe for disaster!
Shooting and hunting with 150 year old rifles would be considered foolhardy by some guys too, and what we're up to here is special gear, special preparation, and special handling.

Further, with consideration of some of the nitro-for-black recipes that are in use for these bore-rifles, there are guys who'd argue that chugging these big charges of black powder is unnecessary and potentially harmful to the rifles!

Any way it goes, my interest is to get one good consistent and accurate load that'll work well in the field in the context of real hunting situations.
As you know the quality of the fouling is half the effort.

On velocities, looking at mid-19th century conversations on 'express' loading, at the "1/4 bullet weight powder charge = ~1600fpsMV" rule, my guess is that I'm pushing or passing the 1600fpsMV mark with the five dram load.

The balls are weighing just about 500 grains.
500/4 = 125
5 drams black powder = 137 grains
The 140 grain charges with the slightly smaller ball shot beautifully, the next load is the ~.690 ball and 140 grains Goex FFg

We shall see.
So far this thing is looking like the "700 Black Powder Express 3 Inch Case"

Cheers
Tinker