Pressure goes up with a longer bearing surface. Bearing surface is the area of the bullet that comes in contact with the barrel. Bullet construction has an effect on pressure also. Pressure may go up with thicker copper jackets or jackets of different materials. Sierra has 4 different lead alloys used for the core of there bullets. The harder alloy used for MatchKings will raise pressure when compared to a Blitz bullet, if the bearing surface is the same.