A Balancing Act…

Norbert Nimrod hovers glassy eyed in front of the shotgun display at the local gunshop. The proprietor enthusiastically touts the benefits of the latest London “best” Smythington Chutneygout sidelock or pigeon pounding Spaghettini Porcini over and under. The spiel invariably includes the seductive, “Just feel how this fine gun handles. See- the balance point is right over the hinge pin.”

Friends, trust the Technoid when he tells you that there is more to gun balance than Nimrod is being shown. Drawing heavily on the assistance of G.T. Garwood (the Technoid’s patron saint), the effort required to swing a gun depends upon its moment of inertia as measured about its point of balance. You can hang a brick on each end of a broom stick and make it seesaw where you will, but you could not call it properly balanced. Good gun balance is dynamic, not static.

Look at the broom stick and brick example. If a brick were tied onto each end of the broom stick, it would balance right in the middle, but would be very hard to swing about due to having the weight at the ends. This demonstrates high moment of inertia.

That same broom stick, with the bricks moved close together in the center, would weigh exactly the same and balance in the same place. However, due to the center weighting, the stick would have a very low moment of inertia and would swing about with abandon.

Traditionally, the British game gun places the balance point and most of the weight between the hands. This gives the gun a low moment of inertia resulting in good speed and maneuverability, especially suited for field shooting. Americans have usually opted for a somewhat more muzzle heavy bias. This increases steadiness and is generally thought better for clay targets, which do not change direction suddenly.

Balance is quite subjective, but there is a range of general preference. If you like the way that your gun feels, consider yourself thrice blessed and stop here. If you have found the dynamics of other guns preferable to yours, you might consider some modest changes.

If your gun feels a little muzzle heavy and sluggish, like many of the long barreled O/Us with screw chokes do, you can either add weight to the rear or eliminate some from the front. Reduce nose weight by shortening the existing barrels, substituting shorter or lighter barrels, or by backboring the barrels. Backboring can remove a surprising amount of weight and is the best approach. Removing wood from the forend may help for an extremely subtle change.

Adding weight to the butt may also reduce the muzzle heavy feel, but too much can drastically alter the moment of inertia. It is best to add weight to the stock by stringing it out along the inside of the stock, rather than just adding a clump at the rear. Unfortunately, the former approach often requires the assistance of a stockmaker. If you do not need too much weight at the rear, some lead plumbers wool in the stock cavity would be worth a try. It does not take much weight addition to subtly change the feel of the gun.

If your gun is too light up front, like many small gauge Continental guns, it is difficult to aesthetically add weight to the barrels. You can take one of three basic approaches. First, you can remove a small amount of weight from the stock by enlarging the stock cavity. Secondly, you can cut hollow pockets inside the forend and fill them with lead. Thirdly, and of limited application, you can install a set of sub-gauge tubes. Do not clamp a skeet shooter’s weight onto the barrel. It adds the weight all in one spot. You will not be happy.

Generally, be forewarned that the balance and feel of a gun are built in, not added on. Subtle changes in balance and moment of inertia are practical, but it is wiser to trade the gun if a more extreme alteration is required.

Bruce Buck
Shotgun Report’s Technoid
(Often in error. Never in doubt.)

This entry was posted in Technoid's Technical Tracts and tagged . Bookmark the permalink.

1 Response to A Balancing Act…

  1. Dirk DeRooy says:

    Plumber’s wool in the stock? I’m a novice, but I recall reading years ago about a case where a stock had been split by corroded plumber’s wool in the cavity. Urban myth? Maybe, but it sure sounds plausible, and not something I would risk.
    That said, I enjoy your writing
    Best Regards,
    Dirk DeRooy


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