Gunsmithing: Shotguns. Patrick Sweeney
Читать онлайн книгу.
according to how you are dressed. The poor duck or goose hunter, bundled up against typically goose-like weather, finds that he (or she) is not shooting the same shotgun used for practice. At least that's how it feels. And the gun certainly doesn't feel like the same shotgun that fit so well at the gun club or gun shop. What to do?
Checking for fit
Before you go cutting on a perfectly good stock you should determine if it fits or not. And if it does not fit, determine where it needs to be changed and by how much. The trial-and-error gun club method can work quite well, but you need an experienced observer to spot your shot cloud. Unless the observer can see your misses and where they are in relation to the clay pigeon, you won't know which direction you are missing in. I once spent a very frustrating afternoon trying to get a shotgun and load dialed on. My observer was having a heck of a time. The range was snow-covered, and there was a heavy and low overcast. He couldn't spot any of my shots, and I finally had to use trial and error to determine how much lead I needed for that load.
To check fit you need a stationary target. Otherwise the number of variables becomes too great to handle. The fitting check is called the Churchill method, after the British gunsmith who developed it. On a target stand or pattern board, mark your aiming spot with a dot of a couple of inches in diameter. Stand exactly 16 yards from the target. The distance is important, as it determines the correction you will make on your stock. Use a tape measure if you have to, but get it exactly 16 yards.
Face your target in your shooting position, but with the gun in low ready. When you feel ready, raise the shotgun and shoot without aiming. Don't rush the shot, but don't take your time and aim. You will have a hit somewhere near (we hope) the dot. Lower your shotgun and assume the ready position. On your second shot, forget where the first hit was. You do not want to “correct” your hit on the second shot, you want the shotgun to come up and fire the moment you are comfortable. If you slow down and aim, you defeat the intent of the exercise.
When I was first exposed to the Churchill method, it was explained to the as “a method of checking gun fit.” It is also a method of checking the consistency of your presentation. If you fire five times and the patterns are all in the same spot, you are either aiming or consistent. If your five patterns are all over the place, your presentation is not consistent, and altering the stock will not make any difference in your shooting.
Trap guns and slug guns can come from the factory with a raised comb. The higher comb gets your eye higher to raise the trap pattern, or place your eye in line with the scope of a slug gun.
You can add drop to your stock if it is a Mossberg. These spacers go between the stock and receiver.
To measure pitch, place the butt flat against the ground and the top edge of the receiver against a vertical surface such as a wall or door jamb.
With the spacers in place, the angle between the stock and receiver changes. More drop makes it more comfortable for some shooters, less for others.
A rubber cheekpiece not only softens the impact to your face, but raises the pattern against the bead.
Grip curve has an effect on how you hold your elbow. The Remington stock, above, will force your firing hand elbow lower than the Browning stock, below.
The grip diameter can be good or bad for your shooting. If too large, it is awkward and tiring. If too small, there is no place to comfortably place your hand, and trigger control suffers.
If, for one shot, the shooter mounts the stock out on the shoulder…
… and the next time mounts it in the shoulder pocket, his pattern will be delivered to a different place. Consistency matters.
In the Churchill method, start with the gun down, a measured 16 yards from the target.
Assuming you have a consistent presentation, then we can work to alter the stock. Plot the centers of each of the five patterns, and come up with an average of their centers.
The Churchill method gives you a change to work with. For each inch the common center is from the dot, you need to correct the stock by 1/16 of an inch. In fitting a stock to strike the dot, the two important dimensions are comb height and width. Changing these two will move the pattern. Changing other dimensions alter comfort in shooting, but have little effect on the location of the impact of the shot relative to the dot.
Length of pull
Length is the easiest dimension of a stock to measure, and probably the one that matters the least. Changes in stock length do not correspond to the Churchill 1:1/16 ratio. So long as you can get the stock up without snagging your clothes, it is short enough. If it keeps your thumb from bumping your nose, it is long enough. Somewhere in the middle there is a length right for you, but that “right” length can span more than an inch of different stock lengths. Shotgun stocks are too long for many shooters. A longer stock feels good at the gun shop, and the proportions look right. Get out in the duck blind with layers of wool and wind-proof synthetic on, and that stock will be at least an inch longer than it was in the gun shop. A stock that is too long makes it harder to reach the trigger and forearm, makes mounting it to your shoulder clumsier, and moves your eye farther down the stock. Not only is the shotgun harder to use, but with your eye farther back, the gun will now deliver its pattern to a different spot than it did when you tested in shirtsleeves. When you practiced at the range, you wore a shirt, or a lightly-padded shooting jacket. With all the winter clothes on, you aren't hitting where you were then. It may not make much of a difference, but all the small changes add up. Test it as you will use it. If you are going to use your shotgun bundled up like and Eskimo, then that is how you should fit-test it.
Bring the gun up and fire without aiming. You want the gun to feel good, but not spend time guiding the bead.
To shorten a too-long stock requires the right equipment. You have to cut the stock the amount you want without chipping the wood, and re-fit either the old pad or a new one. At the very least you need a belt sander or a disk sander secured to a bench. A radial or table saw with a carbide-tipped blade is a big help. If you don't have either, or access to them, then shortening a stock will be an ordeal. (Sorry, but there is no way to sugar-coat it.) Shortening your stock may be something you want to take to a professional gunsmith. Shortening a synthetic stock is sometimes not possible at all. Many synthetic stocks are hollow, with the recoil pad screws fastened to threaded metal inserts in the plastic. If you cut the plastic, you cut off the inserts, and now have no place to attach the recoil pad to. The Remington 1100 is another troublesome stock. The recoil spring tube