Bill,
The answer would be dependent on just how much too long the stock is and whether it is too long for an adult or a child.
Generally speaking, a stock with a parallel comb that is too long would tend to be awkward to more difficult to swing accurately. Stock length is also dependent of the correctness of the stock's drop at the heel dimension and the height of the gun mount. A stock that is too long would also promote a poor gun mount with the head and neck tilted or leaned too far forward, with their accompanying problems. There would also be a tendency to mount the gun too far out on the shoulder and/or rotate the stance too far in the direction of the side of the gun mount, i.e. a rifle-like stance.
If using a field stock with a rising comb, consistent gun mounts would be difficult. The cheek could be placed on a part of the comb at varying distances below the rib and introduce the possibility of differing cheek pressures if the shooter checks the front and mid bead aliment following every mount. Too much or too little cheek pressure is not likely to remain the same during swings and would result in varying vertical points of impact.
For younger shooters the problems are exaggerated, with the addition of a tendency to put too much weight on the back foot, possibly to the extent of introducing cheek slap.
Rollin
