JS- Excellent choice, the GPR is without doubt the best deal going in a traditional BP rifle, actually looks like a real Plains rifle unlike just about all the other factory Hawken types, and your rifle will shoot better than just about all of them as well. Once you get some loads worked up you'll be shooting as well as any custom rifle. GOEX would be amongst my personal last choices of BP, but it's dramatically superior to Pyrodrek, clean or clear shot or any of the rest of that crap.
The Hornady balls are great and CCI caps are considered the best for
most, I'd also recommend getting some .495 balls they may be slightly more accurate, now or later on when your barrel has a little wear, as far
as the patches go it's not a bad idea to go to a fabric store and buy a yard each of 2 or 3 different thiknesses of pillow ticking tear them in strips slighly wider than your muzzle roll up the strips 1 in each thickness then saturate the roll in a good patch lube and put them in a plastic box margerins tub etc so they wont dry out or get contaminated with any abrasives then try the different thiknesses with different daimeter balls
once you've established some accurate powder levels, put the end of
one of the strips over the muzzle short start the ball with the nub on the short starter just enough so that it clears the muzzle the use a very sharp
small knife to slide accross the top of the muzzle and cut the patch be sure to align the material the same way every time, consistency is the key to fine accuracy in BP shooting, you'll have patches that are superior to the commercial ones if for no for other reason that they are perfectly centered every time which is darn difficult with the pre-cut ones, once you've determined the best combination of patch thickness and ball diameter go back and get a few yards of that particular ticking and you'll be saving a great deal of money over time and doing it the way that it was done back in the day, get or make a good patch lube the best IMHO
is LeHigh Valley Patch lube I get mine from Thunder Ridge
http://www.cap-n-ball.com/thunder/index.htm#mainmenualso get some cider vinegar or non ammoniated glass cleaner, windshield
washer solution etc as a cleaning solvent and a load of cleaning patches
for cleaning the barrel after shooting these or even plain cold water are
pretty much superior to just about all the commercial ripoffs like T/C#13
which is 90% water and 10% silicone it's a lame patch lube and no better a solvent than plain water, get a bottle of rubbing alcohol to remove any residual moisture from your barrel after you're wet solvent patch and dry patch cleaning is over, and some quality oil like LPS II for regular between shoots barrel preservation and LPS III for protecting the barrel
between seasons. Don't fall for the bore butter bore seasoning thing it's BS the stuff is just basically lard with a chapstick like wax and the BP salt residues will hapilly rust the bore microscopically under that crap, lots of guys have been doing that for years and they'll show you thier shiny bore
but if you sectioned their barrels or looked in there with a real bore scope you'd see flake rust and pits in the pores, particularly if they're doing the bore seasoning thing with Pyrodrek. Same goes for the almost universally accepted practice of cleaning the barrel in hot water and detergent in a bucket it'll do the same thing, rust in the pores. Your barrel's accuracy potential will last several times longer cleaning and preserving it the way
I've described, and not only will the home made route actually work better but you can use all the money you've saved for buying new rifles, shooting more, going hunting etc, let all the anal retentive yuppie pidgeons get burned.
I'd also recommend getting a good stainless steel range rod with a brass or nylon centering button and use it, the rod that comes with the rifle is for hunting or decoration and will get coated with abrasive dust and screw up your muzzle crown in short order barrel steel is actually much softer
than most think. also get a breech scraper to remove the crud that builds up un the breech face, I think the GPR has a patent breech so get a .32 cal one to get down in that cavity and a .50 for the surroundding breech face area, also get a couple of steel shanked jags the brass shanked ones will bend or break easily.
If you've got a local shop that sells this stuff buy it there unless they're really pirates, as most of the skinflint types will perhaps get a LB of BP or some caps get all kinds of help from the guy and then mail order everything, the main reson there are so few BP oriented shops the price differential isn't much.
You can find tons of great information on this site and others like it, an excellent book I'd recommend is Sam Fadalla's Black Powder Loading manual.
You might also look into joining a BP shooting club in your area, as you can get a LB or 2 of BP for the wholesale price, and you'll learn a great deal as most BP shooters are happy to help a new guy and many of the clubs are older greybeards like myself and interested in new blood to keep things going, I shot BP off and on for over 20 years and then started shooting with a club and then learned more in 6 months than in the past 20 years. Don't be afraid to ask any question because you think you'll be thought of as an idiot, we all were newbie's and asked all kinds of dumb questions, or were actually too dumb to ask and did truly dumb stuff like
ruining barrels or even getting hurt. This time of year most of these sites
are quite dead so many of us appreciate seeing some traffic. Have fun shooting the GPR.
Regards fredj