Don't know why folks think guns/loads that killed well 150 years ago can't do it now.
The ligher load and smaller calibers back then were no more effective than they would be today. But, the big difference is today we have good medical care. 'back then' even what we would consider just a wound would likely be fatal.
As to the original question. Yes, it can be done. But ranges need to be very close, like no more than 25 yards. And, unless you are a well practiced shot with the Dragoon, I say leave it at home. If you don't know what charge to use that suggests you are not a very experienced shooter with that old timey style banger.
If you are determined, use as much real black powder as you can get under the round ball without crushing it.