When you use the Pellets have you been putting the (Black Igniter End) down the Barrel first? The pellets have this black end on one side to supposedly give better ignition to them. Both Loose Powder and Pellets can go bad if not properly stored right, they need to be kept away from humidity and heat. Pellets usually go bad first.
Also Loose Powder also has it's advantages, with loose powder you can shoot a load other than just 100gr's or 150gr's with the 50gr pellets or 60gr,90gr,120gr150gr with the 30gr 50 Cal Pellets. In other words with loose powder you find your load that shoots best out of your MLer it could be from 80-110gr's of powder or anywhere inbetween, you cant do this with pellets. And whenever possible use a 209 primer with Pellets.
(BP)