RE: Why blackpowder doesn't shoot as fast as a rifle?
If you compare a black powder rifle to some of the old 45/70 cartridges (not some of the new ones out there) you can get pretty close to those speeds, and in some cases even better. Those rifles killed thousands of buffalo and other game in our growing country.
We do not shoot a caliber normally smaller then .40 caliber. Most shooters are shooting .44 & .45 caliber projectiles. That is much different then the .30 calibers and smaller. Also as stated, the black powder burns a lot different then modern smokeless powder. It produces a total different barrel pressure burn.
All we can do is understand our differences and adjust our shooting situations to match the bullet we use and our skills. Much like a bow hunter. We normally get one shot. We know what the weapon will do. And we adjust for that kind of a shot.
What I find more remarkable then the fact most muzzleloaders can not match speeds, etc of the bigger modern center fire rifles is, even those that use a roundball, can still be very effective and deadly in their hunting experiences. We go out with (in many cases) limited range abilities, limited knock down abilities, and a one shot deal, yet are able to harvest most anything on the planet.