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OK, surfed around and it looks like some shoot mini's and some shoot RB. .570 seems to stand out as a standard, but it seems like .562 would be a good size. I thought the general rule of thumb was if using .010 cotton patching, then one needs to back off on the OAL size exactly that much on the RB. Are most using .005 cotton patching and using .570 balls? Or does it make that much difference, just use the proper patch for the ball being used. Still on a learning curve, but want to do it halfway right.
TIA
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When it comes to rifles, most folks use a ball that is .010 under bore size, but start with a .015 patch to fill in the rifling grooves. If the barrel has deep groove rifling which is usually deeper than .010, then a .018 pillow ticking patch can be tried. If a .015 patch loads too tight, then switch to the .010 patch and compare the accuracy results. A percentage of the extra patch material gets compressed when it's rammed, so the little extra thickness fills in the rifling grooves, and helps to impart spin to the ball by helping to grab it better when it's fired.
A .005 patch is almost like not using a patch at all. It's very thin, will not hold much patch lube, may tear on loading and ramming, and may cut, burn or frey with a moderately heavy powder charge. The .005 patch is usually only used alone if absolutely necessary because of an extra tight bore or a if a larger than ideal ball is being used.
They are often used in single shot pistols with light powder charges, or in combination with another patch to increase the overall patch thickness to help fill in the rifling if a better patch thickness isn't readily available.
Rifles usually prefer to be loaded with a tighter patched round ball for better accuracy and less patch blowout will occur, especially with the bigger bores using higher powder loads.
So start with a .015 patch and a .570 round ball unless there's a looseness problem or deeper groove rifling, or using round balls that are undersized for the bore diameter. Rifling is almost always at least .005 deep, and more commonly .007 -.010 deep. So try to fill in the rifling grooves with compressed patch material upon loading.
Using lubed patches is also helpful.
