Lateral displacement of the patterns, left or right, is in the realm of cast. A pattern that impacts to the left of the dot for a right-handed shooter needs to be moved to the right using cast off. Impact to the right of the dot dictates cast on for a left-handed shooter, or less cast for a righty.

Cast is subtle, normally 1/8 inch to 1/4 inch at the heel and about an additional 1/8-inch cast at the toe to better fit the butt into the shoulder pocket that runs diagonal from the top of the shoulder to the arm pit is all that’s necessary. For example, off-the-rack Berettas normally have 3.5 mm (3/16 inch) cast off. Cast off or on is tough to accommodate on a straight stock, but it can be done. The cheek-side of the stock can be dished out, but that’s impossible on a synthetic stock. However, on a pump or semi-automatic one can remove a bit of wood or plastic from the head of the stock on the side the cast is moving to, and then make some shims from stiff cardboard—shell-box cardboard make good shim material as does thin brass available at hobby stores—that are fitted between the stock and receiver to accomplish cast.

Once you have a good idea how your stock is fitting you, it is a good idea to record these dimensions. Little more than a yardstick and ruler are needed. With the shotgun in a vise, cleaning cradle or other secure means, hold the yardstick on top of the rib and then using the ruler, measure from the bottom of the yardstick to the top of the comb at the front and rear, and record the measurement. If your patterning found changes necessary, make note of them and add those changes to the data taken from the gun—then you have your own set of stock dimensions. Should you at some time want a custom stock made, you can supply these dimensions to any competent stockmaker, and he will produce a stock just for you.

Those manufacturers whose stocks accommodate shim kits can make achieving adjustments easy. The shims are not finite stock-fitting cures, as they only move the stock so much. If your dimensions are on the wide side of average, you may need to do some additional work, but for the now average shotgunner, they come pretty close.

The shims fit between the front of the stock and rear of the action. To access them remove the recoil pad—some require a screw driver, normally a Phillips, but the Benelli Super Black Eagle II’s pads snap off—then using a deep socket wrench of the proper size (13 mm services Beretta and Benelli guns), remove the stock, then exchange the shim for the one that best approaches your needed dimensions and replace the stock. Changing the shims on the Remington Versa Max is even easier. The dimensions for each shim are listed in the instruction manual. The shims work in tandem with the steel plate in the buttstock, and it is necessary to carefully follow the instructions in the owner’s manual to get it right. Fitting the metal plate over the stock bolt in a Benelli or Beretta can be a little exasperating—I use one of those magnetic rods mechanics use to retrieve dropped parts. Once the shim is in place, and the metal plate positioned, simply reinstall and tighten the stock bolt—do not overtighten it, just be sure it is good and snug. Most manufacturers specify a torque value for the stock bolt.

Once the stock is adjusted, go back to the range and re-shoot the targets to be sure your gun is doing the most important thing, shooting where you are looking.

Adjusting a stock can take time, but with easy-to-use shims and some range time, your percentage of hits can rise dramatically. Whether you have a new shotgun or want to make the old one shoot better for you, take a good look at that bag of shims, they’re there for a very good reason.