Fun to shoot right?
You’ve left out a few details:
- Bullet diameter?
- Bullet temper (hardness)?
- Bullet lubed with proper Black Powder lube?
- “not regulating”...meaning what....shooting apart?, crossing? (I’d guess shooting apart)
- individual barrel groups are OK, or shooting all over the place.
- ever get a good measure of groove diameter?
- chronograph velocities?
- wiping between shots or blow tube?
- powder charge....just poured, drop tube, or powder compression? Weighed 137 grains or 5Drams by BP measure?
- bench rest or off sticks? Hand between forend/barrels and whatever it is rested on?

Just a start and important to know.
- Mike

EDIT: I see Tinker beat me to the keyboard by a couple of minutes