Actually, what appears to be smoke in front of the ball or bullet on film taken of any gun firing is much more likely compressed air from the barrel, together with moisture droplets, and any oil or other foreign substance that is vaporized by the high velocity pressure in front of the ball or bullet. Both oil drops and water drops will give the appearance of " smoke " just as steam coming up out of a chimney looks like " white " smoke. The difference between the two is apparent in how quickly it dissipates after leaving the barrel.
Real smoke containing mostly carbon debris, will remain visibleand float down wind in the light breeze, where water and oil droplets will quickly dissipate, and " disappear.". The oil drops to the ground, and the water returns to vapor in the warm, drier air.
A good OP wad does a very good job of sealing gases behind the wad, and you should expect to see a velocity increase by using the wads under a PRB.