Hello, I think there are some very experienced cast bullet experts over on the Shiloh Rifles forum. These folks shoot Black Powder Cartridge Rifles (BPCR), and shoot tons of lead every year. The .405 is very, very similar to the .40-70 they shoot. Shiloh also makes the Sharps 1874 in .405. There is a lot to be learned from those folks.
Also, for bullets I'd recommend Harlan's Sage Brush bullets. He makes a great Snover in .40 that may just work for you. If not, he can give you a good steer. These are available lubed or unlubed (his Alox lube is excellent!), and sized or unsized, in 1-20 or 1-30 formula. Very honest guy with a good product. Overall, I just wouldn't plan on pushing the lead too fast compared to jacketed.
Have you thought of loading black powder? It is a lot of fun, and a cinch to clean up with a No. 1 (it all goes out of the muzzle). The Windex with Vinegar works great as a cleaner. The recoil would be next to nothing with black, and you'd probably get around 1200 fps with a 400+ grain lead bullet as a guess. Other know a lot more than I do.
God Bless, Marc