Winchester Cases
35 grains, or thereabouts, of 2&1/2Fg or Cartridge grind Goex (essentially the same thing, I just mix my own). Don't bother weighing it, it is a waste of time. Technically what you do is shoot the same volume of black powder as occupied by 35 grains of water. That is the old black powder system. Otherwise just find a load in that range that fills the case to a desired level, as below. Lots of guys use the Lee dippers, and that is good enough. 50 percent of your charge will not be burned inside the firearm, so don't waste your time on weighing the charge.
250 grain standard bullets with a for sure, real, black powder lube. Bullets should be relatively soft, if you can get them. Black powder loads usually do not lead like smokeless and softer bullets will shoot better with it, about 1:20 Tin:Lead should be about right. That is the classic number. Measure the cylinder throats on your revolver and make sure that the bullets are at least as big as the largest throat. Otherwise just shoot 0.454 inch bullet. Some oversize will not hurt: soft lead bullets squeeze down easily. If you can afford it, get the RCBS Cowboy dies. They have an inside expander that is meant for 0.454 inch lead bullets and it really is better to use it. A real black powder lube will keep your gun functioning longer than that hard wax stuff.
Winchester Large Pistol Magnum primers, or regular, as you see fit.
Heavy roll crimp, done right please.
Whether or not you drill your flash holes is up to you. Some do and some don't. I do, especially with the heavily compressed loads (I shoot 40 grains or 20 grains of black plus enough instant gritts to fill the case to the same place). That requires a heavy compression with a separate compression die so that you do not deform the bullet when seating and compressing at the same time. If you do not want the extra operation of compression, then just put in enough powder so that the bullet compresses the powder 1/16 inch or so--otherwise excess compression will ruin the bullet.
Allow no air space in the final load. Period.
Hope that helps.