TH44,

Even though I said I wouldn't use a faster powder than 4198 in the snider there are other powders with similar burn rates that may ignite better. Also IMR4759 is one of my favorite powders but it does have a fast burn rate similar to shotgun flake powders. It is a bulk powder. I have not used this powder in big cases so I won't tell you to try it. I think Gramme Wright had some information on pressure tests in his new book.
Vintage guns are fun to shoot but you need to be careful.

Sam