The problem with the .357 in short barrels is not loss of velocity -- it's that as the gun gets lighter, recoil impulse increases. A gun writer whose name I forget at the moment said, "With light-weight revolvers made from exotic metals, gunmakers have managed to change the .357's recoil from merely unpleasant to downright painful."
By the way, short barrels don't burn less powder -- by the time the bullet is in the forcing cone, all the powder is burnt. From that point on, expanding gas drives the bullet.
If you find unburned grains of powder, it's not because of the short barrel, it's due to incomplete combustion, usually traceable to inadequate bullet pull.