With my 38-40 I have had good luck using 2400 powder. Might look at load data using that in the 44. Graf & sons has brass every once in a while.If you pick up any old brass, make sure they are not the Balloon Head types.
Also do some research into serial numbers as to what ones were suitable using smokeless powder and not BP. If it is truly a 1906 mfgr you are probably ok. I'd still check though.
Definitely slug the barrel. Look to Dardas Cast Bullets as they have the capability to size cast bullets to what you need within reason, ( .001-.003 over sized of bore)
