Well, presuming that you are loaded jacketed bullets, and knowing that smokeless powders are just that, smokeless......
I would suggest that maybe your crimps aren't tight enough. We get this question ALL THE TIME.
The crimp does a couple of things. It keeps the assembly together during firing (with all that recoil, if it wasn't crimped, the parts would loosen up, and bullets typically go deeper into the cases). It also holds onto the bullet a little longer, allowing the powder to fully burn inside the case, allowing only gas to push the bullet out.
If your crimp isn't tight enough, the bullet will start on it's journey early, allowing burning powder to also travel down your bore. When it does that, a couple of things happen.
1) You get a LOT of smoke
2) Your gun gets very dirty and sooty
3) The bullet travels SLOWER than expected, because the powder didn't burn completely in the case, giving the bullet the full force of it;s expansion from the case to the muzzle.
So, as has been offered up many times, here's my tip for checking how good your crimp is:
Fire a round or two, at a blank piece of paper, from a distance of about 8 feet.
If you get only a round hole, the crimp is good.
If you get a round hole with a dark gray spiral pattern around it, the crimp is too loose. The dark gray spiral pattern is powder residue caused by burning powder, traveling down your bore.
Let us know how your testing goes.