I agree that we are talking about the same thing. However, I think it worthwhile to clear up some differences.
Guns are fixed objects and do not change their shapes. So, their dynamics are also fixed. Each and every gun will have a weight, balance point, unmounted swing effort (the relation between the amount of effort expended by the shooter and the change in direction the gun points while the gun is held between the two hands), mounted swing effort is the same as unmounted except that the gun is mounted to the shoulder and point of rotation is now near the butt. The fifth factor, compactness, is predictive of the relationship between the guns weight and it's swing efforts.
Each part of the gun contributes to weight and each part's weight plus its location determine how much the part contributes to the gun's swing effort.
Balance is determined by the linear equation of weight times location. Swing effort (moment of inertia) is weight times location squared. Weight distribution is much more important in swing effort than in balance.
DDA
