If you are thinking of buying a new one, look at the Knights in a western config, anything from the Bighorn up to the Ultra Light in a 50. The older TC Black Diamonds shoot pretty well in a western config also.
Disc Extreme is a great middle ground. Have an older Disc Extreme that is an absolute tack driver with pyrodex pellets and copper 358 power belts. Too bad they changed all the rules on us and I cant use it now. The Bighorn I currently have does not like the all lead PB's at all. Now that they have an Idaho legal Disc Extreme, I will be ordering one in the next couple weeks for a second ML this fall.
Most of the new inlines will have a 28 twist, so you are looking at bare conicals in the 380 to 460 grain range. Look at No Excuse bullets out of Utah. They sell a 420 and a 460 that shoot well in 28 twists. If it's a Knight, try the .503 diameter first. Affordable at $28 per 50.
I really like the old Shockeys Gold powder from American Pioneer. Loads very easily after many firings, cleans super easy and it doesnt stink! And best of all it doesnt seem to be nearly as corrosive.
Just some advise that has helped me. When working loads, mount a fricken scope on it. Then there is no doubt what shoots and what doesnt. Trade in the fiber optic sights for a peep on the rear and a globe with inserts on the front. Best upgrade on any of mine. In between each shot, spit on a patch and run it down the barrel, turn it over and run it down again to somewhat dry it.
For what its worth... YMMV.