is to protect the pellets, and that is something a flat cardboard disk from the early 1900s could not do.
The Deci-Max is designed for extending 10-gauge versatility with lightweight shot charges and small shot sizes. It is pre-slit and recipes are available for this wad with lead, bismuth and Hevi-Shot.
The Competition Special 12-gauge wad from BPI is recommended for high performance shooting value on sporting clays courses. It features a double-crush section of “G” ring to cushions pellets during the setback phase of a shot.
Hevi-Shot requires wad columns or shotcups specifically designed for loading and shooting Hevi-Shot. The TPS 10-gauge shotcup series represents a culmination of many convergent technologies.
Once the shotcup has exited the barrel, it falls away quickly. Most modern wads are designed with petals so that the shotcup opens like a flower, the sides folding quickly backwards. Air resistance causes the shotcup, its petals now open like a parachute, to fall behind the pellets almost instantly. The wad usually falls to the ground within 10 to 15 yards, having completed its mission. (Older or experimental shotcups without petals often fell to the ground with some pellets remaining inside!) Un-slit wads (i.e., those without precut petals) are available, but with the intent that the reloader will slit them to a particular load and pattern preference.
What the old style flat disks could do, however – and what special disks can still do (refer to some of the recipe notes) – was to provide bulk when needed as reload recipes for powder and payload changed. Only one shotcup is used in a load today, but felt or cardboard wads can still be stacked if necessary when shell components change.
In separating the burning powder from the lead shot, the wad or shotcup helps prevent the extreme heat of the burning gas from melting the lead. Lead melts at 621.5 degrees Fahrenheit and boils at 3,164 degrees. According to Mike Daly at Hodgdon, today’s smokeless powders generate heat in the range of 2,800 to 3,200 degrees Kelvin. That computes to a range of 4,575 to 5,300 degrees Fahrenheit. That is easily hot enough to melt your lead shot if the temperature is sustained for more than a few seconds, which of course it is not. It is hot enough to fuse some of the pellets if these hot gases slip around the wad and decide to mingle. Imagine the havoc this will wreak with your carefully constructed shot pattern. Disastrous!
Curiously, reports on Hevi-Shot from Environ-Metal and Remington, show quite a bit of pellet deformation before a load is shot and this has not seemed to disrupt the patterns profoundly. Hevi-Shot is a blend of tungsten, nickel and iron that is actually heavier than lead – and still eco-friendly. This commentary should not be construed as a commercial for Hevi-Shot, only a report about characteristics that appear to differ from the normative expectation, but hunters and load testers alike attest to the lethality of this brand and composition. On the other hand, Kent/Gamebore notes that their Impact brand eco-friendly tungsten-matrix shot is not formulated to improve on lead. Thus, it is not harder than the steel in the typical shotgun barrel and does not require thick, protective plastic shotcups. Kent says its tungsten loads are just fine for fixed-choke guns as well as for sub gauges and guns with screw-in chokes and that these loads have the same “clean killing ballistic properties of lead.”
Another function of the wad/shotcup is to provide a flat, regular surface against which the expanding gases can press outward. A load of shot, even target #9, is porous, and buffered shot, which is only a load of shot whose spaces between the pellets are filled with sifted polyethylene particles, will allow gas to blow through unevenly if the shot is not backed by a wad or shotcup. The wad provides a ceiling against which the hot, expanding gas can press evenly, thrusting the shot down the barrel uniformly.
The wad also seals the gases behind the shotcup in an area of limited oxygen, an element that of course is required for combustion. Thus is the burning propellant limited in its burn rate and only by forcing the shot and wad down and out the barrel does complete combustion take place.
There are numerous shotcup designs from several internationally recognized manufacturers, but your chosen formula will note specific brands and styles: Remington SP16 or WAA 12R or CB 1034-28.
When building a specific load, use the specific components called for in the formula. Why? We have discussed the fact that there are several shell types for any gauge and that even though it might not be immediately obvious, some shells are straight-walled while others have tapered walls. A wad designed for use in a straight-walled Federal hull might not work to seal the gases properly in Winchester’s compression-formed AA hulls that have tapered walls. Winchester and a few other companies make wads with a smaller, angular base to fit these special hulls. In case a wad for straight hulls is used in a tapered hull, it will usually be a little on the large size, so you will have to make sure that your press seats it snugly. (Actually, this is not so rare in load recipes, but it is quite rare that a wad designed for a tapered hull will ever be recommended for a larger, straight-sided hull.)
Using the wrong wad can result in sub-par performance if it results in “powder migration” past the seal, or if significant “blow-by” (gas escaping around a load rather than pushing with all its force behind it) reduces load pressure and velocity. So variances in gas-sealing ability and the different pressures these hulls thereby produce are one reason never to substitute wads.
Most modern wads are designed to “obturate.” This means that the bell-shaped gas seal flares out slightly under pressure to create a self-sustaining seal. Engineers who design shotcups understand that a tight, consistent seal gives your load maximum drive and consistent ballistic performance.
High velocity loads require a tight gas seal in the hull and in the shotgun’s bore to achieve quality results. The modern phenomenon of back-boring or over-boring barrels, enlarging the bore diameter slightly beyond SAAMI standards, has become popular without much consideration of the procedure’s effect on the shotcup’s ability to seal the gas behind the load of shot. Of course, we are only talking about a few thousandths of an inch, a virtually impossible difference for the unaided human eye to distinguish, but it is significant in a manufacturing and shooting environment where the difference between success and failure is often no more than that. If gas escapes around the wad seal in an overbored barrel, velocity and pattern will suffer.
The problem of inadequate gas seal grows exponentially when shotcups from smaller, tapered shells are forced to carry maximum loads through overbored barrels. This is a mismatch, but you can easily correct it at the reloading bench.
As shot loads become heavier than the typical 1-1/8-ounce 12-gauge target loads, propellant charges become bulkier because larger amounts of slower burning powders are generally required, especially for strong hunting loads. As such, the powder charge tops off above the tapered base, rendering a tapered-base wad irrelevant. In such a load, tapered-base wads increase the risk of a poor load without any potential advantage. Consider instead using a wad with a larger, tighter fitting seal.
Today’s wad is essentially a slick, three-part shell element, but the center section – which we have not yet discussed – is as important as the sections on either end. The center is a cushion, in effect, a collapsible spring. Its job is to work like a shock absorber, although admittedly an extremely light one, and to progressively collapse, evenly and uniformly, without tipping and thereby applying greater pressure to one side of the load.
Because the modern wad is a relatively soft plastic, you can see the imprint of the shot in an expended wad. If you
