I concur with Triple Se7en comments, though I think FF powder works just as good as FFF. I read somewhere that FFF in a rifle gets you a little more velocity, but at the price of higher pressure and recoil. The GPR is a heavy rifle though, the recoil from 90 grains of FF under a .50 RB is very managable.

I'd sugget getting a Uncle Mike's Hot Shot nipple for the GPR. Also get a small screw driver and remove the sidelock cleanout screw before you shoot the gun the first time. Coat that screw with some Bore Butter or anti-seize grease and re-install. Remember to remove that screw everytime you clean the barrel. A buddy has the plain Lymans model, a Plains Hunter (I think), and he never removed that screw, it's now frozen in the gun. My GPR is 15+ years old and still shoots as good as the day I built it, never had a miss fire and superb accuracy with a patched RB.

The other thing I would mention is this, if you shoot RBs remember they don't have the downrange power of a saboted bullet or a conical. I've read that the Ball-et has more weight than a regular RB and it's a little harder.

Oh yeah, you can make your own wedge remover with a small piece of dowel.