How to test if your shotgun fits correctly and what to do if it does not.
A shotgun that fits correctly shoots where you look. This allows you to pull the trigger without hesitation when you bring the gun’s stock to your face. You will always be confident that whatever you’re looking at will wind up in the center of a swarm of pellets. Also, a gun that fits is easier to handle and more comfortable to shoot.
Most people pick up a gun, throw it to their shoulder, close one eye and look down the rib. If they can get the bead on the target, they think it fits. For most shooters, it doesn’t, but they are none the wiser. They take it to the field, hit some birds, and miss others then think they need to learn to shoot better. 95% of being on target with a shotgun is gun fit, the other 5% is the amount of lead you have on the target. There is one other aspect that plays a huge role in accuracy: you have to mount the gun the same way every time to hit in the same place every time. A correct gun fit makes this much easier to accomplish.
So, you want to shoot better, right? We owe it to the game we pursue to have quick kills, and the only way to accomplish that is to have a correct fitting shotgun. While a full-scale fitting is a worthwhile experience, you can also fit yourself. An increasing number of Browning, Benelli, Beretta, Stoeger, and Mossberg pump-action and semi-automatics come with shims and spacers that allow you to change the drop, cast, and stock length. With other guns or older guns, you’ll have to improvise your shotgun’s fit adjustments.
Once you've determined whether you need to adjust your length of pull, comb height, or cast, you can follow the instructions in the user manual for stock removal and shim additions. Most shims are reversible and mount between the receiver and stock. Depending on the orientation of the shim, you can obtain multiple fit adjustments using the same shim. Once you place a shim, repeat the comb and cast fit checks to be sure you're on the right track.
Comb Height
The comb is the top portion of the stock where you place your cheek. With the gun mounted, observe how far the stock drops below the bore line. With a proper comb height fit, you should be looking straight down the flat rib on top of the barrel when you mount the gun.
When you shoulder your gun, the rib should be virtually unseen. That means your eye is neither above nor below the line of the rib. If your gun has a center bead, it and the front bead should be perfectly aligned. If the front bead is above the rib or center bead, it means your comb needs to be dropped. If the opposite is true, the comb needs to be raised.
A drill you can do to recognize the need for comb height adjustment is to look at a target in the distance and then mount your gun quickly in its direction. If you have to drop or raise your head to get a flat line of sight down the rib, you need to make adjustments to the comb height.
Adjusting the drop of the stock is equivalent to correcting the elevation on a rifle sight. Drop is the distance from the top of the barrel or rib to the top edge of the stock, measured at the front of the comb and at the top of the butt, or “heel.”
To raise the comb, you should use the factory shims if possible. You can temporarily increase drop by loosening the stock bolt, wedging a small shim between the head of the stock and the top of the back of the receiver, then tightening the bolt again. Use a very thin shim. Even a flat wood toothpick can change the drop of a gun half an inch. If you have an older gun and don’t want to use homemade shims, use Dr. Scholl’s adhesive-backed moleskin to build up the comb until you find the right height.
Cast
The cast is the side to side angle of the stock in relation to the barrel. The cast is the windage adjustment on a shotgun. It’s a lateral bend in the stock designed to center your dominant eye over the rib.
With your shotgun still shouldered, observe the cast. If the front bead is to the right or left of the rib, it means you need to add shims to achieve the proper cast and stock pairing on your gun. As with comb height, you want to make sure the rib is perfectly aligned side to side when you mount the gun. If it's not, you’re going to shoot consistently right or left of your target.
Shooters with wider, rounder faces or narrowly set eyes often need cast, while many thin-faced shooters can shoot uncast stocks (most American gunstocks have no cast, whereas many European guns do). Right-handed shooters need “cast off,” a bend to the right; lefties need “cast on.” If you want to adjust cast on a pump or a semi-automatic shotgun and you don’t have a factory shim use a toothpick shim. Loosen the bolt and wedge the shim lengthwise along the stock head opposite the direction you want to bend the stock. Gunsmiths can permanently cast stocks with hot oil or a heat lamp.
Length of Pull
Length of pull (LOP) is the distance between the front of the trigger and the center of the gun butt. To determine your LOP, mount the gun and measure the distance between your nose and the knuckle of your thumb. It should be about two finger-widths or 1-1½ inches. A stock should be short enough to allow you to mount the gun without snagging it on your vest, but long enough that you don’t have to pull too far back into your shoulder, pulling the muzzle off target. A slip-on recoil pad or spacers can lengthen a stock; a thinner recoil pad can shorten it. If you have to cut it down, be sure not to alter the angle of the butt, known as the “pitch.”
Pitch and Toe Out
Pitch and toe out are aspects of gun fitting that are often overlooked. Adjusting both dimensions can make a gun more comfortable to shoot. Pitch is the angle of the butt pad relative to the barrels. To distribute recoil over the largest possible area, the butt should make full contact with the shoulder pocket. This prevents it from the butt from digging in at the top or bottom of the shoulder or jumping up to slap your face. You can experiment with pitch by backing out the top or bottom screw of the recoil pad and using quarters as spacers to change the angle of the pad. More down pitch (spacers at the top) counteracts face slap; more up pitch (spacers at the bottom) can fix a gun that kicks downward.
Toe out angles the bottom of the butt plate outward and helps shooters who have problems canting (tilting) the gun. A stock with toe out is often more comfortable for women. You can experiment with the angle of the toe by removing the bottom screw of your recoil pad and twisting the pad outward.
Test your fit to see the impact point
Once you have made adjustments based on the above information, it’s time to test and make sure your gun strikes where you are looking. Gun fitters use a 3 or 4-foot square steel plate covered with paint or grease to show pellet strikes when they test a gun’s fit. If you don’t have a pattern plate, you can use a sheet of plywood covered with paper, a sheet, or a plastic tablecloth. Hang it up, make a 2-inch aiming mark in the center, screw in a tight choke, and shoot from 16 yards away. Start with an un-mounted gun and raise it smoothly to your cheek. Focus on the target and shoot the instant the gun touches your shoulder. Don’t correct your aim or look at the bead(s). Repeat this process until a hole appears in the target. If the hole is centered above or below the aiming point, you will have to alter the drop of the stock. If the center is left or right you will want to adjust the cast. Every inch off-center at 16 yards requires a 1/16th-inch change in the stock dimensions.
Another way to easily increase drop and lower the point of impact is to lengthen the stock (note: see the length of pull before you make this adjustment). While increasing the length of the stock doesn’t change the dimensions, it does put your cheek farther back on the sloping stock, effectively increasing drop. To raise the point of impact, shorten the stock. This can be done by decreasing the thickness of the recoil pad. One way to test is to remove the pad and see how it changes the point of impact. One may be able to find the correct thickness for the recoil pad to make the impact correct. It is very difficult to change or cut a synthetic stock, but a wood stock can be cut off to get the correct length. Cutting a wood stock should be done with great care or by a professional gunsmith. A gunsmith can lower the comb by rasping the wood or raise it by building it up or adding an adjustable comb.
For field shooting, most bird and waterfowl hunters want a gun that shoots slightly high, say, 60 percent of its pattern above the aiming point and 40 percent below, this allows you to look at the bird and make the shot. Few prefer a flat 50-50 point of impact that requires you to block out the bird with the muzzle.
Leave a comment