Welcome to the Walker Club. Walker owners are a special Breed of handgunners
I prefer Triple 7 to black powder in the revovers. I would also change the Uberti nipples out for Track Of the Wolf nipples. The number 11 Remington caps work very well. The cylinder removed held under the hot water tap with some Windex sprayed on it will wash most of the chambers out. Follow up with a chamber swab and brush the nipples cleam and wash off with very hot water. Use hot water in the bore with a swab. After all parts are dry light oil with Ballistol or Rem oil. Always pour some 90% alcohol in each chamber and let it run thru the nipples and dry. Using alcohol clean residue from hammer and rear of frame. Put a good lube on the center pin and replace cylinder. As for loads these guns can generate .357 ballistics. The problem is with the 50 and 60 grs. load the cylinders often bind up after a few shots and require a squirt bottle of water to spray front of center pin. Once a year take the gun down and clean and lube it. The Walker was made to fire a "Pickett" or conicale bullet. The Lee 200 grs. Rem. .452 works well for heavy loads. For fun shooting your light round ball loads are fun.