YOu can buy pillow ticking, denim, canvas, pocket drill, and other tightly woven fabrics at most fabric stores. JoAnn Fabrics is one national chain that carried a good selection, and sells the cloth by the yard. Walmart- or, really-- some Walmart Stores still carry fabrics, and many shooters simply buy their fabric there.
Take a caliper or micrometer to the store, to measure the thickness. Check the thickness of what you found working for you in the past, by measuring a patch before going. Better, take the sample with you, to show the sales clerk. Not all pillow ticking-- even with the same color stripes --- is the same thickness. So MEASURE!
The same with your bore, and groove diameters. Groove diameters different with different barrel makers, and sometimes even within the same company my model and caliber of rifle. YOu just have to measure the groove depth, and use that as a guide in choosing the right thickness for your patching.
Land to Land is the " Bore " diameter. Groove to Groove is the groove diameter. Depth of the groove is determined by subtracting the bore diameter from the groove diameter, and then dividing by 2. Most barrels comes with grooves that are .005-.006 deep, but in some Hawken styles, and a few eastern styles, you will find deeper grooves- up to .012" deep! Remember that damp cotton will compress to almost 1/2 its original " dry " thickness, ( depending on the ratio of land width to groove width-- the cloth has to have someplace to go!), so, for example, a groove depth of .006" should allow you to use a patch as thick as .018", depending on what size ball you are using.
My .50 caliber has .006" deep grooves, and I use a .490 ball and .015 or .018" patches. .020" patches are a bit tight! But I can use them, as long as I always clean the barrel between shots, and am prepared to fight to get that patch and ball down the barrel. It goes down- screaming all the way! ( or is that me I hear?????) :rotf: :hatsoff: