Back in the 70s I built a CVA .45 Kentucky percussion. Used it a bit but then got into archery. Bringing it back to life now. But, I read up on all the advances in ML and made some changes. I got one of the new 777 powder and a nipple that uses the shotgun primers. When the trigger is pulled it goes 'Boom" really nice. I also got some Hornady .45 sabots as I succumbed to the ballistic improvement over round balls. So, I shot it today for the first time. In the pursuit of speed I used 100g by volume. The bullets did hit the target at 25 yards but they went through sideways. Would make a really big hole in a deer at that range, but accuracy might suck.

My question is do you think I used too much powder and need to cut back? Why else would it tumble like that?

Not powder.

Your CVA's spout lacks the requisite rpm to spit pointy projectiles. They are twisted slow for patched round balls.

It's a 1 in 48 which is "supposed" to work for both. Not the 1 in 60 for a round ball but certainly not the 1 in 20 or 24 for conicals. Maybe that's it, though.