Pat,
You can still download the manuel from Freedom Arms website which states, where blackpowder is unavailable, bullseye is the suggested replacement. Use of smokeless powders in converted/reproofed black powder firearms is becoming more and more common over here in the UK, where to hold blackpowder you need to apply for an explosive certificate and have specialy constructed boxes to store it in. None of which is required for smokeless powder.
Check it out,
http://www.westlakeengineering.com/4640/4694.html
I'd only ever do it where recommened, with a strong, modern pistol, I do like my hands afterall.
And a lot of our smaller ranges are indoors which isn't good for blackpowder shooting