I experimented with smokeless powder in the Ruger Old Army many years ago using Hercules Bullseye powder. Yes it was that long ago before it was Alliant Bullseye. I still have half a can of it.
It just does not work with #11 caps and nipples. Endless failures to fire and when it does ignite, you get squibs, very low velocity loads that go "poof". The only way I could make it work was to put a small igniter charge of 4Fg, about the amount used to prime a flintlock, in the chamber with the smokeless powder, then is shot quite well. That igniter charge basically did the primer's job in a modern cartridge, to jump the chamber pressure up into the region where smokeless powder burns fast.
That's why smokeless conversions need sealed primer ignition such as 209 shotgun primers.
By the way, I have heard that the 16 inch guns on battle ships are loaded with a 5 kg bag of black powder between the main smokeless charge, about 600 pounds, and the primer. This is called the igniter charge.
One thing about smokeless powder is that low pressure loads tend to be dirty, leaving a lot of unburned powder in the bore. If you want lighter loads, you have to go to faster burning smokeless powder formulations to get good results, both in clean burning and consistent velocities.
I looked up cowboy action loads for the Colt .45 and the recommended powders were Bullseye, American Select, and Unique. Ditto for the .45 Scholfield except the recommended loads were lower due to the cases smaller capacity.
Chamber capacity has a big effect on pressure. A deep seated ball will really jump the pressure due to less airspace for the powder gasses to expand into.
It just does not work with #11 caps and nipples. Endless failures to fire and when it does ignite, you get squibs, very low velocity loads that go "poof". The only way I could make it work was to put a small igniter charge of 4Fg, about the amount used to prime a flintlock, in the chamber with the smokeless powder, then is shot quite well. That igniter charge basically did the primer's job in a modern cartridge, to jump the chamber pressure up into the region where smokeless powder burns fast.
That's why smokeless conversions need sealed primer ignition such as 209 shotgun primers.
By the way, I have heard that the 16 inch guns on battle ships are loaded with a 5 kg bag of black powder between the main smokeless charge, about 600 pounds, and the primer. This is called the igniter charge.
One thing about smokeless powder is that low pressure loads tend to be dirty, leaving a lot of unburned powder in the bore. If you want lighter loads, you have to go to faster burning smokeless powder formulations to get good results, both in clean burning and consistent velocities.
I looked up cowboy action loads for the Colt .45 and the recommended powders were Bullseye, American Select, and Unique. Ditto for the .45 Scholfield except the recommended loads were lower due to the cases smaller capacity.
Chamber capacity has a big effect on pressure. A deep seated ball will really jump the pressure due to less airspace for the powder gasses to expand into.