I've had success with a .015" patch material only with a ball that is the same size as the bore- ie: a .451" in a .45 cal., .400" in a .40 and most recently, a .575" in a .575" bore with only .003" deep rifling.
When using a .440" in a .45, I need a .0215" patch to eliminate any fouling buildup in the bore and to shoot well. With a .445" ball, I use the same .0215" denim patch as it shoots splendidly, however a thinner .020" denim patch will work just fine. The larger ball shoots more accurately - every time.
In the .40 rifle, although the thin, .015" patch will work with the bore sized ball (.400"), they show burn spots so I regularly use a .019" to .020" denim patch which shows no stress and shoots the best of all. Using LHV or Hoppe's 9Plus lube, I get clean shooting, even with loads that might burn or cut the patches slightly.
This was proved last Sunday with the new .58 rifle. New, very sharp rifling of progressive depth and a very tight combination - the .015" patch, bore size ball and only .003" for rifling. Every patch I picked up, had 5 cuts corresponding to the lands, yet none were burnt and accuracy was a 1" hole for 3 shots at 20 yards, offhand. I know it wasn't far but that's where the target happened to be. With 4' or more of snow off the trail, I wasn't about to change that. The only reason the patches seemed to work appears to be due to the very low pressures involved with the squib load I was shooting, a mere 70gr. Even the 92 yard fox target was easy once I found the balls were only dropping 3" below line of sight at that range. Loading never got difficult nor was there any buildup of fouling anywhere in the bore. Hoppe's 9Plus is good stuff.
In summer weather, a tighter combination is required than in cold weather. This probably has to do with barrel heat, therefor powder heat and higher pressures in higher temps. The higher the pressure, the tighter the combination must be. This showed itself in spades a couple years back on the steel silhouette course of fire. I had retested a rifle I hadn't shot for many years, the 14 bore rifle. When I tested it at a close 50yards in early spring, about 35F, a .015" patch worked fine with the light, close range load of 82gr., yet when using that load in +90F weather, I found difficulty hitting the 25 and 50 yards targets, along with about a 6" drop in elevation from where they were supposed to be. On the way to set up the few I'd hit, I picked up a couple of my patches, identified by the radius size and colour. They were fragments. I did notice a slight crusting of fouling ahead of the powder charge in the chamber. After that, I switched to a .020" denim patch & increased the charge to correspond to the longer range targets and had no further problems. The ball for that rifle is .006" smaller than the bore and the .020" denim patch was necessary to shoot cleanly, and return the accuracy. I find it easier to relate a story explaining a similar situation, than merely saying do this, or do that.
Not only do the thin patches promote burnout or cutting, they don' t hold very much lube. The lube used must be exceptional for marginal load combinations.
The muzzle's crown is most important in allowing a tight combination to be loaded easily. In a previous post about shooting, there is a short 47 second video showing loading and shooting a .45 flinter and a 20 bore smoothbore. We are using similar loads, yet both load easily. My combination is a .445" ball and a .0215" patch giving .016" total compression in the bottom of the grooves. Ross is using a .600" ball and .020" patch, which gives .020" total compression in the bore. We have already fired over 50 rounds and neither of us has wiped the bore at any time during the day's shooting. These 2 shots were the last after about 2 1/2 or 3 hours of shooting the trail. We all (up here) use substantial patches, with good lubes. Most of use use a ball that is only .005" smaller than the rifle's bore.
Found the video way back in the pages. The fellow taking the video had to restart- and by that time, we already had patches and balls into the muzzle.
