First, Go to Dutch Schoultz's Website, and order up his black powder rifle accuracy system, for $15.00. It will save you hours of frustration, and teach you how to do this.
You do need to own at least a pair of Calipers. You can buy the "DIAL" calipers through Midway USA< or Midsouth Shooter Supply, for less than $30.00. You really don't need a "digital" caliper, which is about 3 times as expensive, for home use. A digital caliper simply becomes another place to store dead batteries! :shocked2: :rotf:
You can take the caliper with you to the local fabric store. As has been said, learn to close the jaws on fabric consistently, by doing so on known items. Its only through practice that you learn to use any measuring tool correctly. Measure various kinds of paper, for instance, that come through your house each day, from junk mail, to newspaper, to magazine pages. Try notebook paper, and TP. I am serious.
Now, all cotton fabrics compress, when used as a Patch material in your gun. You can expect cotton to compress at least one third of its measured thickness. You need to know the depth of the grooves in your gun barrel, when selecting patch thickness. You want cloth thick enough to fill those grooves, even when compressed.
So, for example, if your groove depth is .010"( 10 thousandths of an inch) , choose a patch made of all cotton, that is at least .015" thick. That way, the material will still compress, but it will also completely fill those grooves. If the ball diameter is .010" SMaller than bore diameter, Land to land, the .015 patch compresses to .010" and then is further compressed more because of the land to land diameter( bore diameter) of your gun. That is what makes the tight fit of patch to ball, even when the patch is lubricated. Lubing the patch helps allow the fabric to stretch, and compress more, mostly by moving extra patch material to the sides and down into the grooves of the rifling next to each land.
Oh, my personal standard, whether using my micrometer, or my calipers, is to close the jaws of the tool on the fabric until its tight enough to offer resistance, but just loose enough to allow the cloth to be slide sideways out of the jaws. I tighten the jaws down enough that I can't move the cloth; then I loosen the jaws slowly, testing the cloth until it begins to move. That becomes my standard measurement for that fabric- provided, it proves to be the same in several places on the bolt of cloth.
If your ball diameter is larger than the nominal .490 for a .50 cal. bore, you may have to use thinner patch material than .015". If the ball diameter from your cast balls is smaller than the nominal .490, you may have to use slightly thicker patch material to shoot the bore.
Then, just to add to the fun of doing all this, a soft lead ball expands, or "upsets" or " obturates", when the gun fires, pushing the fabric sideways even more, and often leaving the cloth weave around the sides of the ball, and distorting the shape of the round ball to show the tops of the lands in the barrel.
In Smoothbore guns, firing PRB, you have an additional problem in selecting the proper patch thickness: You don't have grooves for the fabric to push over into. So, ball size is reduced more than what is usually done with rifles. Its fairly common for shooters to find a ball that is .020" smaller than actual bore diameter, particular in the 24 gauge( .58 cal.) and larger smoothbore barrels.
And, a final problem: We actually ask too much of a cloth fabric patch used in most MLers. Its suppose to lubricate the bore and soften fouling left from the prior shot; its suppose to center the ball in the bore; and its suppose to Seal Gases behind it. If a patch is improperly lubed, or lubed with the wrong material, or if its too thin, or if the shooter is using a hotter burning powder than normal, the patch can burn through, allowing hot gases to cut the lead ball in the barrel, and at the muzzle, so that accuracy goes all wrong!
I have only had very limited success, for instance, using .010" thick or thinner patches in any gun for this reason. I did have a .45 cal. rifle that had very small groove depths, that handled the .010" patch better than thicker patching, and the barrel was short enough that the patch did not have time to burn. But, that has been the exception. If you have a long barrel, small caliber, and are using FFFg powder, or even Swiss powder, which burns hotter, or any of the subs, which burn hotter, its likely that burning patches will be a problem. The same thing seems to happen with large bore guns if a thin patch is used, lubed or not.
So, those are the reasons everyone here is smiling, and telling you that this is a process of trial and error. :grin: :shocked2: There is NO set ball diameter or patch thickness that we can recommend that will be "Perfect" for your gun, unless by sheer LUCK! :hmm:
I have watched and helped shooters with the same brand of gun, same caliber, bought within days of each other, who ended up using different ball diameters, and different patch thickness, and powder charges to get the best groups. Both shooter traded guns and got the same good groups, with each other's guns, so it wasn't the shooters. And, when they tried their own load in the other's guns, groups opened up.
Any recommendation you receive here, or elsewhere just gives you an idea of some place to start that might not blow up your gun. :shocked2: :surrender: The rule of thumb is to begin with a powder charge that is equal to the diameter of your bore. If you shoot a .50 cal. rifle, start with 50 grains of either FFg or FFFg Goex. Work up and down, shooting 5 shot groups from a bench rest, and see what is happening down range. Begin at 25 yds, to get on the paper. Don't be concerned about hitting the bullseye. You are shooting for groups first. You can adjust the sights to move the group to the center of the target later. :bow: :v
When you have a powder charge/patch thickness,/ball diameter/lube combination that seems to shoot well at 25 yds, move back to 50 yds, and repeat the process. Yes, this is probably going to take more than one session at the shooting range. When you have a good group at 50 yds.( one hole that does not get much larger than 2 inches) its time to begin adjusting your sites to "zero " the gun for this load at both 25 and 50 yds. Decide if you are going to use a 6 o'clock hold, or hold dead on center of a target, and at which distance, to zero the load.
Check each Spent Patch, and refer to Dutch's material to learn to read the patches. You can expect to find the patch on the ground between 10 and 20 feet in front of the muzzle. If the range has a lot of ground clutter, rake it off to give you clean ground to better see your own patches. Note the direction and velocity of the wind, as it will affect where your spent patches land.
Some shooters find it necessary to mark their patches with a flow pen, so they can distinguish their patches from others. Its not a bad idea to put such a marker pen in your range box if you shoot at a heavily used shooting range.
If you run into problems, just ask us. We have walked this path you are traveling every time we get a new gun. We tend to be able to shorten up the trip because of "short-cuts" we learn about over the years, but the journey is pretty much the same no matter how experienced a shooter you are. :shocked2: :hatsoff:
