Bowling Ball Dynamics
Does the weight block inside a bowling ball make any difference in performance? High performance bowling balls usually have two piece construction. The inside core (weight block) in the center of the ball and the surrounding cover-stock.
The center of gravity for bowling purposes is the lowest point on the surface of the ball after coming to rest if you were to float it in water. This is normally where the grip is drilled when not using and extra hole. The center of gravity is not necessarily the same spot as the top of the weight block, because cores are not round and uniform but are either symmetrical or asymmetrical and come in a wide variety of shapes. Each brand of ball has a unique core shape and can be purchased with a choice of pin placement (top of weight block) in relation to CG (center of gravity). The distances typically available range between zero and six inches apart. Manufacturers do this on purpose to allow for a variety of bowling ball drilling patterns each one creating a unique imbalance in the particular ball being drilled. The imbalance created by the drilling pattern effects the shape of the ball path as it rolls down the lane. The experienced bowler can take advantage of this fact by knowing how to match up a drilling pattern, bowling ball, and lane oil pattern. Matching up correctly creates forgiveness in shot making and better pin action..
Bowling balls are normally drilled with the cores placed in positions that are imbalanced with relation to the bowlers positive axis point (the axis point at the initial point of rotation when the bowler releases the ball). The unstableness causes axis migration. Axis migration means that the axis point changes when measured at each rotation as the ball is rolling down the lane. Axis migration causes the ball to roll over different points on the surface of the ball as it is rotating down the lane causing multiple oil rings around the ball rather than one oil ring. The constant fresh surface in contact with the lane grips more than an oily surface and causes the ball to hook more overall. Hook can be a good thing in bowling creating more pin action and higher scores.
Bowling ball cores are constructed with different densities as well. Some are center heavy (low rg) and some cores are made with the weight distributed more towards the cover of the ball (high rg). Low rg balls will spin more easily than the high rg balls. A great analogy I heard is where the ice skater with arms tucked in spins fast (low rg) compared with the same skater with arms outstreched spins slowly (high rg). This information can be used to advantage when selecting a ball for a given drilling pattern and lane condition.
For a consistant bowler that knows a little about bowling ball dynamics these things do matter quite a bit.