Today we know to use a much oversized ball in cap and ball revolvers - so there is a ring of lead shaved from the ball when it is seated. A greased wad, like Elmer's felt hat, or OxYoke itself will prevent chain fires- or should. In days of old, chain fires happened more often due to the issue nitrated paper ctgs. issued for the service revolvers.

Couple years ago, a friend bought himself a repro Walker 1847. He found a cheap mould for .440" balls at a garage sale and bought it, intending to use it in the cap and ball revolver.

I told him to measure the chamber mouths and buy a mould .004" larger than the largest chamber mouth - usually a .454" works, .457" for the Ruger. He wanted to save his money for powder and caps so he used the undersized ball- figuring he would patch the balls with cloth like in a ML rifle.

The resulting chain fire was 4 out of 6 loads going off, with the bottom chamber being one of them, driving a ball into the loading rod port and bending the frame.

Some people who will not or can not load a tight ball and patch load in a rifle, obtain somewhat improved accuracy by putting a wad between a patched ball and the powder in a rifle. The reason for their improved accuracy is that the patch helps to seal the powder gasses and flame behind the ball, not blasting past & frying their too-thin patch as was happening before. Escaping powder flame, frying patches from around the ball is not conducive to good accuracy.

The increased velocity is the result of the wad sealing the powder gasses behind the ball, much as a grossly undersized bullet fired in a modern rifle will have less velocity & normally accuracy than one that fits the groove diameter.

HOWEVER - if you use a decent/proper ball and patch combination, there will be NO improvement in accuracy and NO increase in speed over the patched ball in the rifle, in comparison.

In the small bore muzzleloading rifles, like .32's up through .45, as used in my tests with wads, I could not get as good accuracy using wads as without them, just normally patched balls. The difference, ie: accuracy loss was not great, as the group sizes only increased to double normal 50 yards.
Average groups ran 1/2" to 1" with normal patches & no wads while up to 2" with the same patches and using wads between patched ball and powder.

I will note here, I used a 1/10" card wad cut from a monoploy board between the grease patched patched ball and powder back in the 80's & 90's for hunting with my .69 cal. rifle. That 14 bore did not care accuracy wise, whether the load had an additional wad or not, unlike the small bores where any change in loading, changed the accuracy.

The reason for that wad, was to protect the powder from the Mink Oil on the patch - as I thought there might be some contamination. Subsequent testing reveals that those "concerns" were unfounded and thus I no longer use the wads to protect the powder in my hunting loads.

When using 165gr. 2f in the charge, there was no difference in speed nor point of impact, wad or not, even after 6 month's storage as initially loaded. Such tests take time- obviously, usually year after year. Last Sunday I fired off the hunting load that I had loaded in my 14 bore, on the 10th of October, no wad. The ball struck fair, right on the spot the bead covered on the plate. Mind you, it was at the normal Moose range - 25 yards. A moose has a large X ring, so ever a little windage or elevation would not have mattered. As it wasn't he shot struck center and went off without any delay.

If using a small powder charge, like in a squirrel rifle, a barrier wad might be a very good idea if storing the gun with a load and patched ball as happens on farms, etc, if needed to have your smokepole loaded for livestock protection. A modern gun might be a good idea in that instance.

Note, if the gun has been fired at all & then reloaded, it needs to be cleaned. Thus the 'new' load must be pulled or fired off so the ML gun can be cleaned first, then loaded a-fresh if desired.

Note, here, a muzzleloader is not considered loaded, if there is no cap on the nipple, or powder in the pan. With flinters, it is a good idea to stick a quill or vent pick into the vent to prevent ANY migration of powder into the pan. Do NOT dry-fire a flinter that has a charge and ball in the barrel. Even though the pan might be empty, there have been instances where a spark has actually entered the vent and ignited the charge. I have never seen this, BUT - I would not tempt fate in this manner, nor trust my good luck to keep me safe.

edited to add the last paragraph.