I copied this from another forum I frequent withing the Cast Bullet Association, of which I belong. This is the second post and of more clarity and precision, I think. I hope it will lay down what works for all of us here in the North.
We deal with humidity from 5% to close to 100% and temperatures that range from 0F below to in excess of 100F. This pretty much covers the gamut of climate. We see no increased fouling in any of the extremes, BUT - notice that some guns do require thicker then normal patching in etctremely hot, dry climates. We always lube the same - saturated patches & we win matches, attesting to the accuracy we enjoy throughout the temperature and humidity range. NEVER do we see a burning or smoldering patch from our guns - patches are re-usable if we care to pick them up and simply re-lube them. I've shot many local trails with old patches, picked up while shooting on the main range, testing loads or when filing in new sights.
I've used the backs of the legs from old jeans, but prefer to purchase my patch material by the yard or meter. Worn clothing is not as strong as new material. Mattress ticking also makes good patches for many rifles (most of mine) in .0215" thickness. I take either calipers or a mic with me to the store and after acertaining the material is 100% cotton, I measure or mic it. The mic is given a good swirl with the ratchet brrrrrrrrt and read. It gives readings from .0015 to .003" smaller than my 3 sets of calipers. The caliper measurements vary due to differences in the width of the jaws on each set. With calipers, I pinch the jaws togther over the material with my thumb and forefinger and read the dial while pinching the material, just as it would be compressed in a bore. I look for a reading of .020" to .022" with the mic and .0225" to .025" for the calipers. The material should be washed before shooting to remove the sizing - I run a regular wash with the new material, then run it through the complete cycle without soap. Washign softens the fabric and shrinks it to a tighter weave, increasing it's strength. Most materials will lose a thou. or 2 when washed., but some cotton weaves that shrink a lot might gain thickness even though losing the sizing. My ticking did just that, increasing from .0205" to .0215".
Ball size - we use balls that are .005" smaller than the bore in rifles for the most accurate shooting. In my .40 target rifle, I use a ball that is .002" larger than the bore, with a .019" patch. It loads easily with a 3/8" hickory rod. It's all in the muzzle. No - the muzzles of my rifles are not coned - I do not believe in coning as it opened groups both times I tested it in 2 very accurate rifles, a .45 and the .40 match rifle. It would be OK for a purely hunting rifle, although I will never do it again - I prefer guilt edge accuracy, on the range and when hunting. Coning more than doubled group sizes. if coning improves accuracy, it must have been pretty dismal before, is all I can say. One of the guys I shoot with often, has a coned .40 and he cannot easily load the larger ball and patch in it, that I use in my rifle, even though the combination is .002" looser in his bore. Mine is undersized by that amount. The reason might be as simple as a long taper produces more friction, than-does the short 'drawing taper' I put on my muzzles. This is simply a polished machine cut to remove the corners. This type of crown allows very tight combinations that do not cut the patch. I have shot normal groups of 5 shots, retrieving the 1st patch, re-lubing it and using it for each of the 5 shots, just to prove the material and thickness is good. I've come to the conclusion that if the patch is not totally reusable, the material or thickness is wrong. Patches with any burns or cuts are not suitable - or - the crown needs work. Most people err on using too-thin a patch.
Back to balls - for hunting, I suppose a person could use a ball that is .010" small than the bore for slightly easier loading maybe - we see no real difference in loading with our loading techniques and lubes when using the larger .005"/under ball. That means a .495" ball in a .50, .445" in a .45 and a .535" in a .54, etc.
Some factory guns have very shallow button'd rlfing that is less suited for shooting patched round balls than are the more deeply machined, cut rifle grooves. We have had good accuracy in button'd barrels with round balls if using a ball .010" smaller, ie: .490", .440" and .530" when using a thick denim patch of .022".
Some makes of denim list it by weight. If your store lists it this way, get the 10 oz. weight. I use this too and it usually runs .022" to .0225" with the mic, and thicker yet with calipers. It is very accurate in all my rifles as well as other's rifles we've tested it in. Linen, if it can be found thick enough, makes a superior patch material. It is also very expensive. I have heard of people using .010" to .012" patches - we won't even use those for cleaning as they are too thin for that job as well. Flannel is the best material for cleaning paches. Bady diapers used to be the best but are hard to find now a days. A thin patch does not seal the gasses behind the ball, and a thin patch does not hold enough lube to keep the fouing soft.
The Crown, The Crown!
We've found over the years that no factory gun has a suitable muzzle crown - as received. Most all of them have a machine cut angle from wider than the groove depth to the tops of the lands. This leaves 2 sharp angles at the top of the cut to the bottom of the grooves and at the tops of the lands. This sharpness cuts patches and makes the lead ring up when attempting to seat a thich patch with the ball. Rounding this angle vastly improves loading and helps the patch and ball swage or draw into the bore much more easily and without damage to the ball. Emery and your thumb will do wonders for the crown and it takes only a few minutes to do well. Rotating your thumb and rotating the barrel periodically keeps the crown perfectly concentric with the bore's axis.
Patches - why do we use thick patches - well - thicker than what most use. Thicker patches hold more lube - more lube softens fouling making loading easier. Soft fouling also maintains an exact, consistant condtition in the bore making for improved accuracy and eliminating the need for frequent wiping. Fouling does not build up shot to shot. Loading is exactly the same all day long as there is never more than one shot's fouling in the bore & that is easily wiped down by the ball and patch as you load the next one.
To load a tight combination, one must use a short starter. There is no repeated hammering or need of a mallet as some describe their loading attempts.
Lubes - for hunting, we use Mink Oil as sold by Trackofthewolf, or Neetsfoot Oil, or Marmont Oil, or Bear's Oil/Grease. For target work, we simply use a spit patch, or a combination of a few ounces of an oil, mixed into winter windshielf washer fluid. Note that patches must be wet - ie: saturated with lube. No, it will not destroy the powder charge. Licking a patch is not using spit for lube, just as a dab of grease or oil does not constitute a lubed patch. The patch must be wet- ie: saturated. In very large bores, I've used a card wad or extra patch between the grease patch and the powder, when hunting. The .62 and .69 cal rifles do not seem to be negatively effected by the additional patch or wad, however all of my smaller bores are effected by the extra wad or patch - negatively as to accuracy. I do not use a 'wad' in them and the powder seems just fine.
Hope this helps - if not, let me know what's up and we'll try to sort out any problems.
Edited for clarity and spelling/typos
The ball and patch combination along with the rifle particualars follows.
GM .45 barrel 42" long with .450" bore, .010" square rifling at .470" groove diameter. .0215" ticking patch + .445" pure lead ball = .488" diameter minus bore of .470" = .018" divided by 2 = .009" compression of ball and patch per side (all the way around) ensuring a 'sealing' fit of ball to bore. I used the rifle's 3/8" hickory rod - note the loading technique and how easily the rod pushes the patch and ball down the barrel. The video starts with seating the patched ball into the barrel using the short, cupped knob on the starter.