I have a .40 cal. Early Lancaster that I built from Jim Chambers. It is a darned good shooting rifle. I found its favorite load is 45 grains of Goex 3f with a 100% cotton drill patch that measures .018 un compressed and .008 compressed. The ball that I use is made by Hornady and measures 0.395. A Ballistol "dry patch" is my lube of choice. Spit also works well as a patch lube in my rifle.
It is intereasting to note that out of curiosity, I wanted to know how much variance in weight there was within the balls that I got from Hornady. I had three unopened boxes and one from which I had fired a few balls. I weighed each box of balls on my Lyman EL-300 electronic scale. The balls had an impressive consistancy in weight. Lot 205059 had a mean weight of 95.4 grains with an extreme spread of 1.0 grains and a std. dev. of 0.3 grains. Lot 99-011 had a mean weight of 94.3 grains, an extreme spread of 0.6 grains and a std. dev. of 0.1 grains. Lot 02-241 had a mean weight of 95.1 grains, an extreme spread of 1.1 grains and a std. dev. of 0.3 grains. From this, I determined that I would feel safe in just using balls straight from a Hornady box without having to weigh them for consistancy. They come from Hornady with the consistancy that I need.
My lube that seems to work best for my rifle is either spit or a dry patch method where I wet the patches with a 1 part Ballistol dissolved in 5 parts water. I saturate the patch material in the mixture, pull it between my fingers to remove any excess and then lay it on an abasolutely flat and level surface to dry. If the surface is not level and flat, the mixture will migrate to the low spots as it drys and the resultant patches will not have an even coating on them.
I prefer to cut my patches at the muzzle but if you prefer to pre-cut your patches, it will make no diference if they are round or square.
Like Rifleman1776 said, it just takes a bunch of carefully methodical experimentation to find the exactly most accurate load for your particular rifle.
Note: I'm trying to type with one bad wing and I seem to manage to get a lot of typos. Please just overlook them for now.