100 grains of BH209 ... how do you determine this? Seriously. Are you doing it exactly the same everytime? Please do so.
How are you pouring the powder? Repeat process exactly each time.
How are you seating the projectiles? Again, do it exactly the same each time. Mark your ramrod to show you where the bullet is just snugly seated against the charge and use that as a guide.
Make sure your breech plugs are clean and clear. Use a 1/8" drill bit by hand to make sure the flame channels are open. Use a nipple pick or similar to make sure the flash holes are clear. You'll need to use the drill bit about every 6-8 shots to keep those plugs clear.
Make sure the bores and the plugs are clean/clear/and dry before loading. Then try to keep them that way. With BH209 it is not necessary to swab after each shot. Your best results might come by shooting a group without swabbing at all OR you might find your best results come from swabbing and drying after every shot.
Be as consistent as humanly possible in every aspect of the loading and shooting process.
Good luck and let us know if things improve.
