First, lay a gun that fits you (or nearly fits you) on a table; then take a straight-edge as long as the gun and lay it along the top of the rib and out over the butt, snug against muzzle and breech. Now measure, as shown below, to whatever dimensions you deem best. By way of illustration I append actual measurements for a man of medium and symmetrical build.
Length from heel to trigger....
____14 5-16 inches
Length from hollow to trigger
Length from toe to trigger......
Drop at comb..................
.... 1 1/2
Drop at heel..................
.... 2 1/2
Depth from toe to heel..........
.... 5 3/8
Length of grip.................
Circumference of grip..........
.... 4 1/4
Trigger to cap of pistol grip-----
.... 4 1/4
Cast-off (explained below)......
In testing for length, it is important to hold the left hand in its most comfortable and masterful position, well forward of the trigger guard, so as to give good command of the gun in any attitude, and yet not far enough to put any strain on the left arm. . The closer one holds to the trigger guard with his left hand, the longer the stock should be, and vice versa. It is the left arm that really governs the proper length of stock, rather than the right.
A short-armed man requires about a fourteen-inch stock; a long-armed one, fourteen and one-half to fourteen and three-fourths. Bend of stock depends upon length of one's neck, and also upon whether he crooks his neck a good deal, in aiming, or points his gun when his head is more erect. In general, it is best to select a rather straight stock, for the express purpose of throwing the shots a little high. Most birds are shot on the rise, and all shot drops in its flight.
A full-chested man requires more hollow in the butt-plate than a flat-chested one.
The comb of a gun affects aim both vertically and horizontally. If its drop is just right for the individual user it will direct his shot at the right elevationóthe comb is, in effect, a shotgun's rear sight. If its thickness just suits the shooter's face, then his eye will naturally follow the center of the gun's rib. In trying guns for drop, hold your head well up, just as you would in the fieldódon't sight down along the rib. Drop at heel, as a rule, is proportional to drop at comb. The usual ratios are: one and one-fourth inch at comb to two inches at heel (short neck) ; one and three-eighths, two and one-fourth; one and one-half, two and one-half (medium neck) ; one and five-eighths, two and five-eighths; one and three-fourths, two and three-fourths (long neck) ; one and seven-eighths, three inches.
If a pistol grip is wanted, let it be of shorter radius (four to four and one-fourth inches) and fuller curve than the present fashion. I can see no advantage in a pistol grip unless the gun has only a single trigger.
Circumference of grip is governed by the size of one's hand. A grip that is too slender cramps the hand, or slips through it when recoiling, and is easily broken in the field.
Cast-off means a sidewise bend of the stock to bring the rib into accurate alignment with the eye. A hollowed-out comb has the same effect as a cast-off to the right. Either of them helps in difficult swinging shots. The amount of cast-off, or shape of comb, is wholly dependent on one's personal build. For average men, a castoff of one-eighth to three-sixteenth inch is sufficient. If you are broad-chested, more may be needed.
A gun balances right when its weight is concentrated near its center of gravity, and when this center is so placed that the right and left hands support equal weight. Such " hang" makes a gun buoyant, makes it feel lighter than it really is, and helps immensely to level the two hands when pointing for a quick shot. An ill-balanced gun is inert, sluggish in the gunner's grasp. A well-balanced one is " alive," responsive. Both weapons may be of the same weight; but one will drag and tire a man, while the other will seem a part of his very self. We all know what it means to say that " the horse and his rider are one "; in the same way should a gun and gunner be one.