Gunsmithing: Shotguns. Patrick Sweeney
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You must be consistent in your gun mount, or a fitted stock will be wasted time, effort and money. If one time you lift your head off the stock.…
If that shotgun is not for sale, you can buy one of the same model or you can modify your gun. By carefully noting the exact dimensions of the shotgun you were hitting so well with, you can duplicate it in your shotguns stock.
…and the next get a solid “cheekweld,” your point of aim will be different with each shot.
The ornate stocks on these wheel-lock pistols were high-tech for their age. Stock design follows the needs and style of the times.
One approach to fitting a shotgun is the “ugly stick” method. Once you have an idea of what stock dimensions you need, you modify a stock to those dimensions. You definitely want to start on a stock that is the plainest of wood. You can use your current stock or you can get a replacement and start working on that. Sand or rasp your stock down, or build it up with epoxy and plastic wood. Practice with it and keep track of your scores. Once you have a stock that fits you, send it off to Fred Wenig. He can duplicate your Frankenstein stock in a very attractive piece of wood, so you won't have to hide your practicegun under a tarp.
You can determine length of pull with a tape measure, but measuring drop is not so easy. To be accurate you need a gauge like this one from Brownells.
What are the critical dimensions of a stock?
Before you go modifying your stock, you have to have an understanding of what each part does. Yes, we all know “put the butt to your shoulder, keep both eyes open and follow through” but sometimes that isn't enough. There are five critical dimensions that matter for fit. They are:
Measure length of pull from the face of the trigger to the center of the buttplate or recoil pad.
(1) Length of pull; the distance from the trigger to the end of the stock at its center.
(2) Drop; the distance down from the axis of the bore, measured to the heel of the stock from the bore or rib.
(3) Comb height; the distance down from the bore where your cheek rests, also measured down from the top surface of the barrel or rib.
(4) Grip pitch; the curve of the grip right behind the trigger guard.
(5) Grip diameter; the thickness of the grip where your trigger finger hand grasps the stock.
Drop is the distance down from the rib or center-line of the bore.
The traditional method of measuring stock length is to compare it to the distance inside your forearm. As a basic method, it is not too bad.
Each critical dimension has one or more less-critical dimensions that can have a bad effect on your shooting if they are too far from “normal.”
Length of pull The length of the stock by itself does not determine where your aiming eye rests, but a stock that is too long for you also probably has too much drop. The excessive drop puts your aiming eye too low. A stock that is too long can also make gunhandling awkward even with correct technique. How long is long enough? The traditional measure is the “elbow” distance. If you can rest the butt of the stock in the crook of your elbow and comfortably grasp the grip, the stock is the correct length. What the elbow test does not tell you is how the gun fits when you are bundled up for the cold.
These two shotguns are lined up with their bores parallel. You can see that the nearer one has more drop. Given the same gun weight and cartridge, the nearer will kick harder.
Cast A minor dimension of length is cast. A stock with cast-off has the butt of the stock out from the centerline. A stock with cast-on has the butt inside from the centerline. Cast on or off depends on which side you shoot from. A stock cast-off for a right-handed shooter is obviously cast-on for a left-handed shooter. For most shooters, cast is not needed, but for some, like very muscular men or curvaceous women, it can be important. Cast in the stock brings the line of the bore to the line of your eye without you having to engage in contortions.
Drop This measurement matters because it effects your shooting style. If you shoot upright with your head erect, you need more drop. If you shoot leaned forward, with your head craned forward to the stock, you need less drop. If you square off to the target, you need less, and “bladed” you need more. A shooter who shoots a shotgun as if he was shooting a rifle at the target range will need a lot more drop in his stock compared to a shooter who faces the target as if it were a boxing opponent.
The Brownells gauge gives you a convenient hole to locate the trigger face against the gauge.
Pitch A minor dimension that goes along with drop is pitch. Pitch is the angle of the buttplate to the axis of the stock and bore. A stock with more pitch will slide up your shoulder under recoil, and strike your face harder than a stock with less pitch. Decrease pitch too much, and the shotgun could slide off your shoulder downwards under recoil, making follow-up shots difficult. A very muscular man has a problem. If he alters the stock to clear his chest (putting more pitch on the buttplate so the toe of the stock does not dig in) he will increase the jump of the stock into his face. The solution is cast-off to move the stock out to his shoulder, and off his chest.
Comb height The height of the comb determines the location of your aiming eye. The stock style known as Monte Carlo is an attempt to keep the eye up while getting enough drop in the stock for comfortable shooting. British stocks do not have Monte Carlo combs because the shooting style is to square off to the target as in boxing. A minor dimension of comb height is comb thickness. A comb that is too thick pushes your face away from the centerline, while a comb that is too thin encourages you to shoot with your head leaning over the stock. Shooting a shotgun with a thin comb hurts, because with your head over the stock, as the stock pivots up it has to push your head out of the way. Instead of sliding out of the way, your cheekbone gets whacked by the comb.
Grip angle The angle of the grip determines the angle your wrist takes upon grasping the shotgun. As the grip angle or curve becomes tighter, your wrist and shooting hand pivot the thumb back towards your face. The pivoting of your wrist changes the angle of the attached elbow. As your elbow moves lower, the “pocket” in your shoulder joint where the stock rests becomes less pronounced. If your elbow drops too much, the butt of the shotgun can move outwards under recoil, and you lose control of follow-up shots. A stock that has a tight curve that starts too close behind the trigger guard hurts your firing hand on recoil. The trigger guard can come back and whack your knuckle during recoil.
Grip thickness A grip that is too thick is difficult to grasp firmly, and can slide under recoil or during mounting of the gun. A stock that is at the maximum for your bare hand can become too large when you wear gloves.
All these dimensions