My 62cal bore mikes out @ 0.617" and I use 0.600" cast balls from Eddie May of GA (~$8 per hundred). I use mink oil lube from Track of The Wolf (TOW - $5 per 6-ounce, 4" round tin) and 'thin' 0.010" thick 'homespun' 100% cotton material from Wla*Mart @ $2/yard.
Even with 70 grains of FFFg, I don't burn through the patches. In fact, I shot the SAME 5 or more patches no less than 4 times each the other day at the range. It was easy :wink: , a crusty snow was on the ground, so I took a break every 5_ shots, walked out, examined them - and then thought "Heck, I'll shoot 'em again!".
I find this combo gives me a great blend of acrruacy and loading ease, with zero to minimal build-up in the bore. Yet, I've always been able to load the next round and I don't swab between shots or after a group of shots. A bonus (for timed events) is I can load it fast!