Rob, try the 'Sky Chief loading' info for straight bored bores:
“Having been asked about the load and its makeup enough times, I will list the recipe here for reference sake.
I'm ignorant in the the ways of posting a link to some of the older threads regarding the load. If any of you are willing and able to do so, all the better. Some are a couple years old, maybe older. It seems some members are having difficulty finding them.
-Powder charge
-Nitro (hard) card
-Shot load
-Thin overshot card
-Full fiber cushion wad*
*The cushion wad needs to be SATURATED (the wetter and heavier, the better) with oil. I like to use olive oil. The load seems to shine best when used in cylinder bored guns.
Best of luck to all, Skychief.”