4198 is a VERY good powder for your 45-70. Thousands upon thousands of rounds have been shot with that powder. you DO NOT need o put filler in there, same as with Rel7 or AA5744. Keep your loads under 40k and you'll be fine.
With the leading soak a patch with turpentine run it down the barrel and let it sit for a few min, the wipe dry. do this a few times, if leading still persists, Birchwood Casey's makes a lead removal cloth, it works very well for removing lead (you will need a stiff rod for this as it will need to be driven through...its real tight!!)
Leading is caused by a few different things, heat, undersized projectiles, crap lube or too much speed/pressure and lead hardness, with your original loading's you probably had 4 of those.... shooting lead is a different animal than copper, and needs to be treated differently. to combat heat (gas cutting) use a gas check, this will also "scrape" any lead left behind. Undersized bullets, there is only one way to make them bigger and your experimenting with that (paint) or, slug your barrel, take measurements and buy the correct size. most of those guns were .450/.458, the .457 most commercial bullets come in are not really good, and with smokeless powder will not obdurate, sealing the bore. The blue lube is JUNK!! its too hard for the pressures/speed your running. You need a softer lube made with better products.
speed/pressure with more pressure you have more heat and need a harder bullet, with a harder bullet you need better lube to combat leading.
Shooting lead has a bit of investment costs but, if you shoot enough and/or shoot lead in different cal's will make this sound better. Buy a lead pot (lee, lyman,RCBS) to start get a bottom pour. get a good mold (Saco, RCBS, Lyman, BACO) of the correct size, with a gas check, get a lubersizer (magma/star, RCBS, Lyman) and the correct die, I would run .459 dia, get some gas checks, and start making your own bullets. Every time you make one your costs are going down per bullet vs buying them. lead can be had at many different places indoor/outdoor ranges, wheel weights from cars, old x-ray labs, sheet lead from roofers, lead pipe (the joints have tin in them) DO NOT......one more time, DO NOT use lead from batteries!! Tin for making it harder can be had from Roto metals.
If you get a good lube, gas check and a properly sized bullet, you can shoot them 1800-2000fps no problem, but its going to take a bit of work to get there. There are a few different lubes that will even allow you to run upwards of 3k fps. #2 lead is a good place to start when casting, watch some video's and get the Lyman cast bullet book, it will explain more than I can, and probably better.
If your interested in paper patching just holler I have been shooting PP bullets competitively for a decade or so and have a few molds for that. Shooting PP bullets in a lever gun, will be tricky though.
Matt
