I have a Swinburn's Patent Martini in the process of being restored. It's chambered for the .450 No. 2 Musket cartridge.

I recognize that this is a black powder cartridge, but I'd like to find a smokeless load that would work in the rifle. Can any of you suggest a load or a source for such a load?

Thanks.

I use 4198 (H or IMR) in my BPE rifles.
IMR4198 seems to be a grain or two below H4198 for the same velocities but they are very close.

The No.2 Musket will fall in the 35-45gr charge weight depending on your bullet weight.
I do use foam baker rod, 1/2" in the 500/450s, and magnum primers.

You can make cases from 50/90 Sharps brass quite easily.

I use 32.5gr of Somchem S335 in a lathe-turned (reduced-volume) case.
I also use the same load in .577-450.

Not sure if that helps.