Originally Posted by blindarcher
....I have read that seating bullets deeper in rifle cartridges decreases both pressure and velocity...
I think you've got that backwards. Seating a rifle bullet out to a longer length allows more room in the case for the powder and ignition, lowering pressure, unless more powder is added to fill that space.
In pistols the shell length is limited by either magazine or cylinder length. Most pistol bullets have a cannelure grove that sets the seating depth and allows the bullet to be crimped to prevent recoil from causing the bullet to withdraw from the case and jamming the weapon.