SharpShooter- what range were you shooting at? When all else fails, move up to 25 yards, so you can hit paper each and every time. Also make sure you have a good solid rest when testing bullets. If this is free hand shooting that could be a lot of your problem. Also how old is your powder and what kind of powder are you shooting?

Start the rifle off with 50 grains and a patched roundball at 25 yards and see what it does. I realize that this seems like very little powder but the point here is to see if it will shoot a group. If it does, start kicking up the charge 10 grains at a time.

Also you mention a lot of crud. Are you talking about fowling or actual barrel particals? If the barrel is still that dirty after all the cleaning you have done, perhaps you need to Bore Paste it, and worse comes to worse, a gentle lapp of the barrel.

I have yet to see a Renegade that will not shoot roundball well. Ball-ets can be a touch and go projectile. Perhaps all it needs is a lot of shooting to smooth the rifle out.