Shotgun Ammunition

From the late nineteenth century until fairly recently, shotgun shells were constructed basically the same way. They consisted of a paper body (the tube); a thin brass or brass-coated steel head; a primer; powder; paper, cardboard or composition wads, and lead shot (Figure 8.1A).

The wads were of four types (Figure 8.1B). First was the base wad which was compressed paper or other material and was located inside the shotgun shell at its base. Its purpose was to fill up the space in the shell not occupied by the propellant powder. This wad was not expelled on firing. The over-powder wad was between the propellant and the filler wads. The overpowder wad was a disk of cardboard that acted as a gas seal and prevented contamination of the powder by grease from the filler wads. The filler wads lay in between the overpowder wad and the shot. The filler wads acted to seal the bore when the shotgun was fired, keeping the gas behind the pellets. In addition, they cushioned the shot against the blast of hot gases, preventing deformation, fusion, and melting of the pellets. Filler wads were greased so that they would lubricate and clean the bore as they moved down it. The mouth of the shotgun shell was closed by a thin cardboard disk—the overshot wad—with the edge of the mouth turned down over this wad in what was called a "rolled crimp."

The brass head of the shell has a rim on it. This rim aids in extraction and head spacing of the shell. In the latter function it prevents the case from moving too far forward into the shotgun chamber.

Until 1960 shotgun tubes were made of paper. In 1960, Remington introduced their SP shell (Figure 8.2a).3 This shell had a polyethylene tube, a brass-plated steel head, and a non-integral base wad, made from an asbestos-like material molded to shape under pressure. In 1972, Remington introduced their plastic RXP shell, which has a solid head section, i.e., an integral base wad that is continuous with the tube wall.3 Originally used only in the Remington skeet and trap loadings (Figure 8.2b), it is now the standard shell for all Remington shotgun ammunition replacing the SP shell.

Winchester introduced two types of plastic shot shells in 1964.3 One was a shell with a corrugated or ribbed tube surface and a non-integral base wad.

Figure 8.1 (A) Traditional shotgun shell with paper tube, brass head, powder, cardboard over-the-powder wad, filler wads, shot, and an over-the-shot wad. (B) Disassembled traditional shotgun shell showing wadding.

Figure 8.1 (A) Traditional shotgun shell with paper tube, brass head, powder, cardboard over-the-powder wad, filler wads, shot, and an over-the-shot wad. (B) Disassembled traditional shotgun shell showing wadding.

This shell was subsequently phased out. The other plastic hull was produced by a combination of injection molding and die forming. There is no separate base wad, with the head section being of solid plastic and continuous with the walls (Figure 8.2c). The Federal Ammunition Company introduced plastic tubes in 1965.3

Although most shotgun shells are now made with plastic tubes, some manufacturers still produce shells with paper tubes. In fact, some competitive skeet and trap shooters prefer such paper tube shells.

Standard shot shells in 12, 16, 20, and 28 gauges are 2 3/4 in. (70 mm) long. This measurement is taken when the case has been fired, i.e., with the crimp unfolded. Unfired, the shells are approximately 1/4 in. (6.2 mm) shorter.

Figure 8.2 (a) Remington SP shell; (b) Remington RXP shell; and (c) Winchester shot shell.

Figure 8.2 (a) Remington SP shell; (b) Remington RXP shell; and (c) Winchester shot shell.

Magnum shotgun shells in 12, 16, and 20 gauges come in the standard 2 3/4-in. (70 mm) length as well as a 3-in. (76 mm) version in the case of 12 and 20 gauge. The standard-length Magnums can be fired in strong modern guns, whereas the 3-in. shell is usable only in guns especially chambered for these rounds. The standard length shell presently manufactured for the 10 gauge is 3 1/2-in. (89 mm). There is no Magnum shell for the 28 gauge. The .410-gauge shells come in 2 1/2 (63.5 mm) and 3 in. (76 mm) length. The longer shell contains a little more extra shot. It is not called a Magnum, however.

The term "Magnum" in regard to rifle and handgun cartridges implies a larger cartridge, more propellant and a higher muzzle velocity. When speaking of Magnum shotgun shells, this is only partly true. Magnum shotgun shells contain more propellant; a heavier charge of shot; may or may not be longer, but they do not produce higher velocities. Rather, the heavier powder charge is used to propel the increased load of pellets at standard velocities. Magnum shells typically have a high brass head.

In 1961, Federal began the introduction of color coding of its shotgun shells.3 At present, Federal shotgun shells are red in 12 gauge, yellow in 20 gauge, and purple in 16 gauge. Remington and Winchester-Western color code their 20-gauge shells yellow; this color coding is done to prevent using the wrong gauge ammunition in a weapon. Use of a 20-gauge shell in a 12 gauge is particularly dangerous. If a 20 gauge shell is inserted in a 12 gauge shotgun chamber, it will slide down into and lodge in the barrel. If a 12-gauge round is then inserted into the weapon and the gun is fired, the 20-gauge round will blow up in the barrel.

Figure 8.3 Low-brass and high-brass shotgun shells.

Shotgun shells often are spoken of as being either low-brass or highbrass, depending on how high the brass head extends up the length of the tube (Figure 8.3). Whether a shotgun shell is high or low brass is not an indication of the volume or strength of a shell. A high head is associated with heavy or Magnum loads; a low head with light field or target loads.

Currently manufactured shotgun shells have brass or brass-plated steel heads. It is possible to produce all-plastic shotgun shells without a metal head. In fact, such shells have been marketed, though unsuccessfully. Other apparently all-plastic cases, e.g., ACTIV, have an internal steel disc in the head to reinforce the rim of the shell and the primer pocket. Winchester states that its compression plastic hull is strong enough to be fired without the metal head, though they do not recommend this.3

By virtue of its design, the traditional shotgun shell had a number of defects. On firing, some of the hot gases from burning powder were able to bypass the over powder and filler wads and reach the shot charge. Here the hot gases partially melted and fused together a number of pellets. In addition to this problem, the rapid acceleration of the shot charge caused pellets at the bottom of the charge to be "welded" together by the pressure into small clumps. Furthermore as the charge moved down the barrel, pellets on the outer edge of the charge that were in direct contact with the barrel were flattened, as a result of both pressure and friction. Thus, by the time the pellets emerged from the barrel, only the central core of pellets, excluding those at the base, were round and undamaged. These undamaged pellets flew "true" toward the target, whereas the damaged pellets and clumps of pellets veered off at varying angles. These are the "fliers" seen in all shotgun patterns.

Another impairment to a good pattern was the overshot wad. This was supposed to slide off to one side of the shot column as it emerged from the barrel. This did not always happen, and the overshot wad sometimes fell into the shot column, disrupting it.

In an attempt to overcome these defects, ammunition manufacturers introduced a number of innovations. The first major change in shotgun shell design was the elimination of the rolled crimp and the overshot wad.3 This was accomplished by introducingthe "pie" crimp. Inthisprocedure, closure of the paper shot shell was accomplished byhavingthetubefolded in a number of equal segments and compressedinwardly to covertheshot column. Thus, the overshot wad was no longer necessary. Federal uses an eight-segment crimp in its plastic shells and a six-segment crimp in its paper shells.

The second innovation was the introduction by Winchesterof the "cup" wad. This is a cup-shaped paper overpowderwadwhosecuppedsurfacefaced the powder. On ignition of the powder, thegasproduceddrivesthelipsof the cup outward, producing a gas-tightsealagainsttheinnerwallof thetube. The cup wad was so effective that it becamepossible to reducethe chargeof powder in the shotgun shells yet obtainthesameballisticperformance. Cup wads are used in most of the shotgunammunitionloaded by Winchester-Western.

In 1962, Winchester introduced theshotprotectivesleeve, orplasticshot collar.3 This consists of a rectangular strip of plastic surrounding the shot charge. The collar acts to eliminate theabrasive-typedamagethatoccursas the pellets move down the barrel. Theuseof suchashot collareliminates lead fouling of the bore and increases thedensityof shotgunpatterns. Plastic

Figure8.4

illustrates a typical present-day Winchesterfieldloadincorporatingthecup wad, filler wads and a plasticshot collar.

In 1963, Remington introduced the Power Piston®.3 The Power Piston® is a one-piece plastic assemblage that provides a cup wad for sealing, a resilient spring center to cushion the acceleration of the shot and a polyethylene cup to prevent the shot from rubbing against the inner wall of the barrel (Figure 8.5). The Powder Piston® eliminates the overpowder wad, the filler wads, and the need for a shot collar. On firing, the gas of propulsion expands the lips of the cup-shaped base outward, providing a gastight seal against the inner wall of the shot shell case. The gas moves the cup wad forward, compressing the plastic spring center between the cup wad and the shot. The Powder Piston® and the shot begin to move forward, breaking the seal at the mouth of the shotgun shell. The shot charge is accelerated down

Figure 8.4 Cross-section of present-day Winchester birdshot shell. (Courtesy of Winchester-Western.)

Figure 8.5 Cross-section of present-day Remington birdshot shell.

Figure 8.4 Cross-section of present-day Winchester birdshot shell. (Courtesy of Winchester-Western.)

Figure 8.5 Cross-section of present-day Remington birdshot shell.

the barrel, protected from contact with the barrel wall by the polyethylene cup and cushioned against the acceleration by the central spring section. The Power Piston® has four longitudinal slits the length of the shot container, dividing the walls of the container into four sections or "petals." As the wad assemblage containing the shot emerges from the barrel, the air pressure acts on the petals, bending them backward and releasing the shot (Figure 8.6). The wad then quickly falls away. Remington Power-Piston® wads are found in different colors apparently due to subcontracting of manufactures. There is apparently no significance to the different colors. Remington uses a variant of the Power-Piston® in some shells where the central portion has a "figure 8"-shaped configuration.

One slightly different approach to the plastic wad construction is the wad assemblage of the Federal Ammunition Company. In 1968, they introduced the two piece Triple-plus® wad column (Figure 8.7).3 This consists of an all-plastic assemblage, made up of a gas-sealing overpowder wad with an integral plastic pillar that acts as a shock absorber (the pillar crushes on firing) and a plastic shot cup that is separate from the plastic wad.

Figure 8.6 Power-Piston® opening up on leaving barrel.

Plastic wads similar to the Power Piston® are now produced by all the major U.S. shotgun shell manufacturers and used in some of their various loadings. Winchester and Federal use a single all-plastic wad with a collapsible central portion in their trap and skeet loads. .410 shells produced by Winchester, Remington, and Federal use plastic shot cups.

Figure 8.7 Cross-section of Federal birdshot shell.

Figure 8.8 Wadding used in (a) Winchester, (b) Federal, and (c) Remington birdshot loads.

Figure 8.8 shows the wadding used in most shot shells manufactured by Winchester, Federal, and Remington. This wadding is not used in shells loaded with buckshot, slugs, or some trap and skeet loadings. It should be understood that manufacturers periodically change the wadding used in their shells, so that many variants exist on the "usual" loading.

In spite of all the new designs in shotgun shells, traditionally constructed shells containing felt or composition filler wads and shells with overshot wads still are manufactured and marketed. In addition, shells manufactured years, even decades ago are still around and may be encountered. Ammunition 40, 50 or more years old is still reliable as long as it was not exposed to extremes of temperature and humidity. This is true for rifle and handgun ammunition as well.

While recovery of a 20-gauge shotgun wad from a body should indicate that the deceased was shot with a 20-gauge shotgun there is an exception. Federal has used a 20-gauge filler wad, inserted in the bottom of a 12 ga plastic shot cup, to prevent low center crimps. Thus, an individual shot with such ammunition may present with both a 12-gauge plastic wad and a 20-gauge filler wad.4

In 1963, Winchester-Western began loading their buckshot shells with buckshot packed in granular white polyethylene filler (Figure 8.9).3 This filler cushions the shot pellets on firing, reducing shot distortion and improving the shot pattern. Remington soon followed Winchester's lead. By the late 1970s, Winchester, Remington, and Federal were loading Magnum birdshot shells with granulated white filler. Filler is now available to handloaders. At

Figure 8.8 Wadding used in (a) Winchester, (b) Federal, and (c) Remington birdshot loads.

Figure 8.9 Winchester buckshot load showing buckshot packed in granulated white polyethylene filler.

close range, this filler can cause stippling (pseudo-tattoo marks) on the skin that can be mistaken for powder tattooing. This phenomenon will be discussed subsequently.

The white filler used in Winchester ammunition is polyethylene, whereas that in Remington is polypropylene. Federal uses both polyethylene and polypropylene, with the latter the most widely used at present.

Examination of a box of shotgun ammunition and sometimes individual shot shells will reveal a series of three numbers such as 3 3/4 - 1 1/4 - 7 1/2. The last number, e.g., 7 1/2, refers to the size of the individual shot pellets; the middle number, e.g., 1 1/4, indicates the weight of the shot charge in ounces. The first number indicates the "dram equivalent" of the particular shell. This is an obsolete term that indicates the comparative power of a shotgun shell loaded in relationship to black powder loads. When black powder was used in shotgun shells, the relative power of the shell was indicated by listing the number of drams of black powder loaded in each shell. The more drams loaded, the more powerful the loading. Modern smokeless powder is rated in dram equivalents. Thus, a certain loading of a shotgun shell will be said to have a dram equivalent value of 3. This indicates that the charge of powder in this shell will drive the charge of shot to approximately the same velocity as 3 drams of black powder. The dram equivalent rating bears no relation to the amount of smokeless powder in the shotgun shells; thus, two shotgun shell cartridges loaded with the same weight and size shot can have the same dram equivalent rating with different quantities of smokeless powder.

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