If these definitions, taken from my book, "Stock Fitter's Bible" are irritating, send an e-mail to firstname.lastname@example.org
telling me to get rid of them. Back-boring/Over-boring:
increasing the bore diameter to reduce perceived recoil, improve patterns and increase shot-velocity. Existing guns can be backbored and new guns may be designed with overbored barrels as one of their features. In use, they amount to the same thingBore:
hole in the barrel through which the shot passes, measured in thousandths of an inch. 12-gauge bores are from .725" to .745" or even larger; nominal is .729".Break point:
point at which a clay target is expected to be broken without rushing the shotButt Stock:
the portion of the stock behind the receiver/actionCast:
distance the stock angles left (cast on) or right (cast off) from the receiver when viewed from the rear. Its purpose is to allow easier and better horizontal alignment of the master eye with the rib without undue tilting or turning of the head.
There are commonly two cast dimensions; the first is the cast at the heel followed by the cast at the toe, usually, slightly greater. This is done to better align the butt with the pectoral muscle forming the inside of the shoulder pocket.Chamber:
breech end of the barrel into which shells are placed when the gun is "in battery" or ready to fire.Choke:
the decrease in diameter of the bore near the end of the barrel; a constriction. Chokes come in many designs, all of which keep the pattern from expanding as quickly at all yardages.Comb:
The top surface of the stock on which the cheek is placed, either parallel with the barrel or upward-sloping (field stocks) in non (clay) target stocksCrooked stock:
All stocks are crooked to some degree. Many years ago, a crooked stock was one with a drop at the heel dimension exceeding 3"; (some were as much as 4".) Today, with the level of the heel still below that of the bore, stocks remain crooked but far less than those used in the past. It is this feature that causes barrels to rise during recoil.Drop at the comb:
Distance from the rib-line (an imaginary line along the top surface of the rib extending to the end of the stock) down to the comb.
On straight (English) stocks (here defined here as those with a pistol grip but no Monte Carlo notch removed at the rear and usually with an upward sloping comb,) two drops are given. The first drop, where the cheek is placed is the "face drop" at the comb and the second drop dimension is to the top of the recoil pad or butt plate, which is actually the drop at the heel. The difference of the two drops lets you know how steep the comb is on the gun.
On Monte Carlo stocks, the drop at the comb dimension, is the distance from rib down to the front (nose) of the comb. The comb may or may not be parallel with the rib. When the stock does not have a parallel comb, the drop dimension are the "drop at the nose" or front of the comb and the "face drop) at the comb, which is an estimation of the distance from the rib line to the place on the comb where the cheek is likely to be placed.Drop at the heel:
a. Distance form the rib line to the top of the butt plate or the top of the recoil pad (heel)
b. Individual dimension for guns with Monte Carlo stocks: Drop at the comb is the distance from the rib-line down to the front (nose) of the comb. If the comb is parallel with the rib, the specifications will note that the stock has a parallel comb.Forcing cone:
section of the barrel in which the diameter of the chamber holding the shell, tapers over a short distance to the smaller bore diameter. The tapered area in the barrel just forward of the chamber is the forcing cone. 1½” is thought by some to be the ideal length but this can change in the future.Fore-end:
the wood grip attached to the barrel in front of the action or receiver. Fore-ends vary widely in shape from very thin "beaver tail" shapes to much wider and higher shapes that many target shooters prefer.Form/Style:
the complete “set-up” involving stance (foot position), gun mount, body posture including the head and neck, and weight distribution. It is an important rudiment on which to build shooting skills. It also has a major afffect on well fitting stock dimensions.Gauge:
Technically, the number of pure, round, lead balls required to weigh a pound.Gun-mount:
the act of bringing the gun to the shoulder; also the position of the gun on the shoulder along with that of the hands and trigger-arm when ready to call for a target.Heel:
the top/upper surface of the recoil pad or butt plate (and the second drop dimension given for straight stocks).Length of pull (LOP):
the distance from the front center of the trigger curvature back to the vertical center of the recoil pad or butt plate - slightly over 14” on many stocks). Line-of-sight/Sight-line:
an imaginary line from the pupil of the eye to the front bead. It indicates the height of the eye relative to the rib and shows the relationship of the center bead (if one exists) to the front bead or the amount of rib seen (if any). The higher the eye is relative to the rib, the higher the center of the pattern will be above the gun's point of aim.Monte Carlo stock:
a stock that has a “notch” removed at the rear. It exists to position the top of the recoil pad (heel) farther below the comb without increasing the "crookedness"/slope of the stock. Its purpose is to compensate for the length of shooters’ necks.Palm swell:
a bulge on the off side of the grip to fill the palm and allow a more secure hold by the trigger hand making gun mounting easier, more secure and precise.Pattern:
the distribution and quantity of shot, within a 30” circle, from a shell commonly fired from a distance of 40 yards. The choke constriction is the major determinant of a pattern but the selection of reloading components plays a small part as well, especially the hardness (antimony content) of the shot used, which reduces the number of "flyers" or shot pellots flying outside of the pattern.
Forty yards is often used as a basis of comparison but more useful information is gained from patterning a gun at the distance where most game is killed or targets are broken. It is best done to learn the POI (see below).Pitch:
the angle formed by the gun’s barrel or rib and the end of the butt or recoil pad, usually near ninety degrees. In this country pitch is often measured by standing a gun on its recoil pad with the action/receiver in contact with a vertical surface. (For a basis of comparison, a 28-inch barrel length is used.) In Europe, pitch is measured in degrees, which is more accurate and more difficult to determine.
The gun’s pitch is the distance from the end of the barrel (or at the 28-inch point) to the vertical surface. The difficulty of this type of pitch description is that action and receiver length plays a part in the pitch distance, which is usually neutral or negative/positive depending on the definition of "positive" pitch being used. (It's all rather esoteric and describing pitch can be problematic.)Point of impact (POI):
the vertical and horizontal center of the pattern at a given distance, usually 30-35 yards in trap shooting, 21 in skeet, and considerably farther in Sporting Clays. POI is the topic of discussion when someone asks, “Are you shooting where you look?” In other words, “Is your POI what you were expecting?” Guns are said to shoot 50-50, 60-40, 70-30, etc. These numbers refer to the percentages of the pattern above and below a horizontal line through an aiming point usually at the distance at which targets are broken.Porting:
a brake; the creation of holes through which gas escapes in the top half of the barrel near the center or more commonly, near the muzzle. The escaping gas slightly reduces barrel rise during recoil and in so doing, often irritates squad mates with an increased noise level when the ported gun is fired. Rib-line:
Line along the top of the rib extending rearward over the heel from which drops at the comb and heel are measured.Recoil:
Phase one involves the rotation of the gun around it center of gravity; the phase two involves the gun's movement to the rear and the upward pivot of the barrel from the shoulder when the gun's rearward movement is stopped or slowed dramatically by the shoulder.Shooting Form:
The shooting style used by a shooter consisting of the stance or foot placement, the gun mount and the body/head and neck posture used by the shooter. Shoulder pocket:
the depression formed between the shoulder joint and pectoral muscle. It is easier to locate when the elbow is raised so the upper arm is parallel to the ground in trap shooting and nearer 45 degrees for other shooting disciplines.Sight-line:
An imaginary line running from the pupil of the eye to the front bead indicating the position of the eye relative to the ribSight picture:
the relative position of the front bead and the target at the moment the gun is fired. Swing-speed is important when creating a sight picture as is the distance to and the direction of the target. Stance:
Position of both feet during set-up, prior to calling for a target.Straight stock:
As used here, a stock with a pistol grip but no Monte Carlo notch removed at the rear. (Also a stock with no pistol grip similar to those on old Winchester Model 94s. These were originally designed for double-barreled shotguns with two triggers to allow easier movement of the hand to the other trigger for a second shot. They also offer the choice of barrels to fire first.Swing speed:
the barrel’s rate of movement when overtaking targets. It is most affected by the position of the hand on the fore-end, (towards the rear is faster when the gun is moved incorrectly by the forward hand instead of with body rotation). Swing speed is slowed and more swing precision is gained when the fore-end is held in the hand nearer the front. Swing speed can also be affected by the stance. Wider stances can slow swing speed.Toe:
"Pointed" bottom of the recoil pad opposite the heel. Broad and rounded toes are preferred over more pointed toes. Wrist:
Section of the stock forward of the comb nose.