Consider black powder only...
Generally on my Shilohs...
I have two Shilohs, the first one I got is a 45/70 Hartford model (standard oct. 30" barrel), and during the waiting time from when I put in my order (less than 2 years on mine), I started acquiring what I needed to shoot the rifle solely as a B.P.C.R. When I got to Big Timber to get the rifle, Kirk Bryan gave me a tutorial on the basic care and feeding, and also gave me a box of 50, 530 grn. Saeco bullets, already greased. I already had all the rest of the stuff needed to load my own rounds. Also during that build waiting time, I was lucky to have buddies who gave me loading advice, and when I finally took the rifle to the range, I had good ammo, and a good time shooting it, along with the blow tube I made, which you'll need if you shoot grease groove bullets. Or, what's big now, is the wiping between shots procedure. I cast my own alloyed bullets these days, but that's a whole other discussion.
As has already been mentioned, get on the Shiloh forum (register so you can do the search engine) and you'll find ANYTHING you'll need to know regarding the care and feeding of a B.P.C.R., especially a Shiloh. And BTW, I got my Hartford back in 2001; my hunting Sharps, and it's proven itself in the field many times.
You've got a beautiful new rifle, and FWIW, t'were me, I'd wait before shooting it until I got the proper, well made ammo that it deserves to run through it, and that's black powder and cast bullets. Personally, I DO NOT use any kind of brush through the bore; lots of cotton patches, with the proper jag, instead (and bore guide in the chamber). I forget what the solution ratio to a gallon of water is as I type this out, but I use the vinegar based Windex all purpose cleaner in a gallon of water; works very well, but just plain water works very well for basic fouling in the bore, too.
For lead removal, and you'll have some to deal with regardless what some will say, study a bit and try some things before you settle on a lead removal product. I bought a good supply of Shiloh Creek Bore Solvent years ago, and find it very very good "to get the lead out." I believe they're out of business now, and when I run out, I'll have to find another source for solvent.
Those Sharps rifles were designed to shoot b.p. and lead alloy bullets. That's all I shoot in mine, and find it very accurate doing so. When shooting these types of rifles accurately, it's all about the right sized bullet/bore combo and powder fouling control, and that's just my opinion, nothing more. Wiping between shots, or blow tubing, and moisture in the air (or lack of it), is what you deal with when shooting a shot string on the line. And that's nothing more than my opinion, too.
I also have a Shiloh Long Range Express in 45/90 cal., and it weighs a bit over 12 pounds. I use it exclusively for a couple of matches on gongs out to 1000 yds. during the summer. With my loadings of b.p, and cast bullets for the rifle, doing my part off of cross-sticks (it's all about the wind), that rifle and load will consistently hit that 1k gong.
Work up a b.p. load for that fine new rifle of your'n, you won't be disappointed. The great thing is, you can looking at and fondle the thing while you're researching proper load data to feed it properly. There's not much more pleasing in the shooting world when you build proper ammo for a Sharps rife, and find it just as accurate as most anything else downrange.
And also as has been mentioned, be sure to bring the rifle to half-cock after firing before dropping the block. It's just a good habit to get into as you follow this trail with your Shiloh. I've been fortunate to have some good shooters who've given me good info during my initial learning curve; I hope the same for you. Have a great time with that new Shiloh, they are beautiful things. BTW, too, I turn 68 this year... maybe that's why I'm rambling a bit here...
) so not a Garand and a half, more like a Garand and a third, though not quite.
