I'm new to the Huntsman also. Got my first one this year. Haven't made anything bleed with it yet, but I'll try again tomorrow. Not the gun's fault, just my novice deer hunting skills that leave a bit to be desired.
So far, I've used Pyrodex pellets (2-50gr) with 245gr SJHP bullets/sabots and Pyrodex P loose (70gr) with Hornady Great Plains 410gr flat nose conicals. At the range both are accurate and consistent. The sabots with 100gr seem to shoot flatter, but I'm leaning toward the loose powder and Great Plains conicals. I put two wonder wads under the bullet after the powder is loaded. Only took a few shots to zero the sights, I don't like scopes except on my .243 for coyotes and .22 for far-sighted squirrels.
Take a tip from one of my other posts' replies. Don't use bore butter with 209 primers and Pyrodex pellets. Makes a huge crud ring near the breech plug. The jag got stuck in the chamber when I tried to clean between shots.
As far as blow back I assume you mean smoke out the breech when firing. I get a little puff from the primer when shot, and a little whisp of smoke when pushing the jag in to clean between shots. Nothing bothersome. I like this thing as it is not a side hammer with all that hardware hanging out and it looks more traditional than the in-line types. I don't like the safety aspects of the in-lines when compared to being able to pull the hammer back on the Huntsman. I'm probably full of bull, but it makes me more comfortable. That's what it is all about.
Good luck and keep fishing for advice here.