[Jbar4Ranch]

Your SWC's will work safely, but BP loads tend to be better with the heavier bullets. Lots o' lube is recommended to keep fouling soft, but most modern bullets don't have large enough grease grooves for extended shooting without the revolver binding up. There is also a big difference between lubes designed for smokeless powder and those designed for black powder.

Black powder is measured by volume, rather than weight, and you aren't going to get 40 grains in a modern solid head .45 Colt case (with a 250 grain bullet anyway). From 1873 to about 1882, the original internal Benét priming system that was used would also have prevented the full 40 grain charge from fitting too. In about 1882, the priming method was changed to an external primer fitting into a pocket in the case head just as we see today, but the case heads were "folded" and had a slightly larger internal capacity than today's cases.
Use a measure that will fill the case to at least where the base of the bullet will be when seated; compression of the powder is often desirable, and perfectly safe - perhaps up to about 1/16". Empty space between the powder and bullet base is undesirable, but won't create an unsafe condition unless excessive - for instance 1/16" will be fine, but having half the case empty can be dangerous. Err on the side of safety and use a compressed load.

Clean the bore, cylinder, and frame with hot soapy water, dry thoroughly (compressed air is good here), then use an oiled patch through the bore and chambers.

Original BP factory rounds of the 19th century are claimed to have been in the 900 fps range with a 255 grain lead bullet from a 7 1/2" revolver barrel... damn potent medicine by any standard.