MB - The balance point can be referenced to any point on a gun. The issue for selecting a reference point is to aid in defining the % of weight carried by each hand. To calculate these %'s, we need the weight and the distance from the center of each hand to the balance point. Rear hand to (front) trigger is a fixed relationship gun to gun. Trigger to hinge pin is not a fixed distance, varying as much as 2" from gun model to gun model. Therefore, hand to hinge pin can't be a fixed number and must be considered on a gun model by gun model basis; note also that pumps and semi-autos don't have a hinge pin but are subject to balance. All guns can use trigger to balance point with the same meaning for each gun-shooter.
Example of balance caluclation: assume hand spread is 12 " center to center, balance is 4" to trigger, and rear hand center to trigger is 3". Then, rear hand center to balance is 7" (3" + 4" = 7"). % weight carried is the inverse of the distance. 12" - 7" divided by 12" = 5"/12" = 0.42 X 100 = 42%. The front hand is, then, 100% - 42% = 58%. Gun weight multiplied by the % gives the hand weight. Ratio of front to rear is by individual preference.
Bushmaster - less than 3" balance to trigger is very rear balanced, 3" to 4" is rear balanced, 4"-5" is "usual/normal/typical" for game weight guns, 5" to 6" is forward balanced, and over 6" is very forward balanced. From my database, the following guns have 6 1/2" balance:
Beretta 391 Gold Semiauto
Remington 1100 auto
L. C Smith "F" TLHG
Beretta 391 Auto
Remingtom M-870 TB
Rizzini Vertex w/ extended screw chokes
Browning Gold Sp Clays Auto/merc
Ithaca NID 4E BLE Trap #457465 SST
Neumann BL 10 bore
Hope that helps. Questions?
