Yes, you need a powder measure that is suitable for black.
There are a number of them.
Lee dippers come with updated tables for Pyrodex and GOEX as well as FFFg, FFg, and Fg.
[This is what I use...but, dippers are not adjustable]
For an adjustable powder measure, CVA and TC a
Cabelas has quite a selection.
http://www.cabelas.com/cabelas/en/templates/pod/horizontal-pod.jsp?_DARGS=/cabelas/en/common/catalog/pod-link.jsp_A&_DAV=MainCatcat20712&rid=&indexId=cat20819&navAction=push&navCount=5&parentType=index&parentId=cat20819&id=0003249Just about any adjustable measure will work.
You don't NEED a drop tube, but, if you want to play with heavier loads, its a good thing to have. I made one of out 1/4" copper tube from HomeDepot and some 2x4" boards for support. My funnel at the top is just a Lee powder funnel hot glued in place. 40" tall and helps with 38-55 cases.
For 56-50, all you really need to do is fill the case about 1/4" below the rim with FFg or FFFg and then seat the bullet on top.
At most, you can get 50gr of FFFg in it. Which is why I guess a few folks have resorted to using Pyrodex 50cal 50gr "pellets". Do NOT use 777 pellets... those are way too hot for the 56-50. 777 is "warmer" than swiss.
FYI: Back during the civil war, Spencer carbines and rifles were stress tested with max loads and they found that by overcharging to 65gr of powder with repeated use would damage the breach. A 50gr pellet of 777 is more like 60gr of BP. So, you are skirting the limit.
"Original" 56-50 bullets had between 35-45gr of BP. IT really depended on who manufactured the cartridge as well as the bullet. (Winchester tended to load a bit lighter, some loaded as much as 50gr...)
Today's spencers are well made with excellent metalurgy and it has proven to be one of the strongest actions out there. The brass from Starline is a solid base variety and has excellent longevity.