Never used the pure copper 240 grain from Buffalo Bullet Company, but if they make them they are probably a good projectile. I like their products.

As already said, lots of people shoot Pyrodex P because it does burn cleaner and it pressure spikes a little faster then RS or Select. Just cut your load back and then work your way up from there. Some of my favorite loads are around 100 grains of the 3f grade powders...

Lets us know how those Buffalo Bullets shoot. I will have to keep an eye out for them. Although I just orders almost $100.00 worth of bullets today, so I am sure I will have plenty to shoot, and will hear all about my hobby....