An All-Star Cast
As far as shotgun stock dimensions go, after pitch, cast is the most misunderstood. The correct cast can make your gun an all-star, but the wrong cast will make you see stars.
Cast is basically a sideways bending of the stock so as to better align your dominant eye over the rib. When viewed from the rear of the gun, cast-off is a stock bend to the right. Cast-on is a stock bend to the left. This is true whether the stock is being bent for a right- or left-handed shooter. Usually a shooter will want the stock bent away somewhat from his face. For a righty, this is cast-off. For a lefty, cast-on.
Cast is sort of a European thing. Most commercial-grade American guns are straight and have no cast either way. Like taxes, this should inconvenience lefties and righties equally. Most production European guns come with cast-off suitable for the 85% of people who are right-handed. A lefty must order a special stock. Naturally, high-end makers make the stock for you and give you whatever you wish.
The whole point of cast is to permit the dominant eye to line up correctly with the rib. If you are right-handed and your gun shoots to the left, you may need more cast-off. If your gun shoots to the right, you may need less. Like the rear sight on a rifle, the direction in which you bend the stock moves the pattern the same way. A stock bent to the right moves the pattern to the right.
What determines cast is: 1) your physique, 2) your shooting style and 3) the style of the stock.
1) Shooters with a thin face may not need any cast. Those with a full face might well need some because the extra flesh moves the dominant eye too far to the side to line up properly.
2) Shooters who shoot more across their body, somewhat like a rifleman, many not need cast because their heads are angled into the stock. Those who mount the gun closer to 90° to their chest probably will need cast to bring the eye over the rib. The broader the shoulder, the more cast.
3) A stock with a thin comb is less likely to need cast than one with a very thick one. Stock thickness itself is a form of cast.
Cast is usually not the same at the heel (top of the butt) as it is at the toe (pointy bottom of the butt). Usually the toe is cast more than the heel to account for the fact that a shooter’s shoulder pocket isn’t vertical. It slopes in more at the top and out at the bottom. Cast should take this into account.
Cast is normally measured at the butt in inches from the centerline of the rib. Fairly standard cast might be 3/16” at heel and 3/8” at toe, but it is really an individual thing. Custom-stock makers may also take cast measurements at the comb nose and face (partway back where your face touches the comb).
The easiest way to quickly check the cast of an unloaded gun is to hold it by the muzzle, turn it upside down so that the butt heel touches the ground at about 45° and look along the underside of the barrels to the stock. Any bend in the stock will be very clear. It’s much more accurate than looking at the gun from the rear.
To the extent that adjusting the cast helps the gun fit you, it is good. Of course, the downside of cast is that any bending of the stock away from the straight line of recoil can increase face slap. It’s all a compromise between pain and performance.
And that’s the last stone I’ll cast today. Boots off. Beer open.