Yep, I bought a Pietta-made 1858 Remington in .36 caliber a little over a year ago.
In my office hangs a target: four round balls you could cover with a quarter, two opening the group to half-dollar size.
Customers come in, read the notes on the target, and are usually shocked that a cap and ball revolver is capable of such accuracy. Many people are surprised to learn that the old revolvers had rifled barrels!
Anyway, here's the particulars on that target:
Shot at 25 yards from a benchrest.
24 grs. Goex FFFG black powder
.380 diameter ball made by Warren Muzzleloading of Arkansas.
Remington No. 10 cap
Ox-Yoke Wonder Wad soaked in a 19th century bullet lubricant recipe, composed of paraffin, mutton tallow and beeswax.
Add the powder. Seat the heavily lubricated felt wad firmly on the powder. THEN seat the .380 inch lead ball firmly.
No lubricant over the ball is needed. Place a Remington No. 10 cap on the nipple and she's ready to fire!
I have found better accuracy in all of my .36-caliber sixguns with the .380 inch ball, instead of the customary .375 inch ball. In fact, in many original and reproduction revolvers, the .375 is too small for a good, tight fit in the chambers.
Also, the slightly larger ball, when swaged into the chamber, creates a wider driving band for the rifling to grip. Many of today's reproductions have rather shallow rifling and this wider driving band can significantly improve accuracy in such revolvers.
On a side note don't bother with conical bullets. I've tried many different designs, in a variety of .36 revolvers, and never found conical bullets as accurate as the lead ball.