Reloading for Shotgunners. Rick SappЧитать онлайн книгу.
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 pick up a couple after you shoot, you will note the permanent impressions of individual pellets and this testifies to the force of the explosive burn that the wad must accommodate. This is caused by the vertical unevenness of the movement through the barrel. The rear shot pellets move prior to those at the head of the shell and this force shows in the spent shotcup. (For someone who has never quite understood how the inside of a wheel spins at a faster speed but at the same rpm as the outside of the wheel, this is all very mystical!) Perhaps you would expect this since within a millisecond, the pressure builds to around 10,000 psi and the load achieves terminal velocity within a few inches of travel.
The writers of a former edition of this book, Kurt Fackler and M.L. McPherson, likened the effects of the powder burn to a shock wave, causing the bottom layers of pellets to “squash themselves against the upper layers.” This shock, they said, was the equivalent of wrapping a towel around a hammer. The instant of most extreme shock and acceleration, which moves the pellets from zero fps to maybe 1,200 fps, is cushioned.
The Ballistic Products Gas Seal or BPGS helps the powder achieve a complete, cyclic burn, with the net result of consistently higher velocities and fewer unburned grains of powder.
BPGS wads are stackable, versatile enough to use in almost any type of hull and will load a huge assortment of recipes.
Cork wads protect the base of a shotcup in a magnum load. Different shot sizes vary the height of the load, so cork wads are placed beneath the shot. This reduces setback damage and brings the load up to perfect crimping height. These wads are light, dense, flexible and can be stacked to make your crimp just right.
Remington’s 870 Express Deer pump-action is available in every gauge except the 10. Its barrel is rifled so it can shoot slugs and sabots accurately to 100 yards – or even farther, with a properly-mounted scope, plenty of practice, and the right combination of primer and other components.
Heavy loads tend to diminish the effectiveness of the cushion. Heavier loads of shot and heavier loads of powder, compress the wad much more significantly than lighter field and target loads. Thus, the energy wave from the powder’s explosion is transferred more directly and harshly to the pellets. Probably, these heavy loads need additional cushioning in the way of felt spacers and special cushion wads that must be placed immediately below the charge of shot.
When reloading, you want this center section to compress, but not collapse. A total collapse would ruin its value and could perhaps damage or torque the gas seal. So, under the steady pressure of the wad ram, the cushion section should predictably compress to accommodate various powder heights.
We have spent quite a few pages discussing wads without mentioning the spreader or brush wad. These wads are usually made with no shotcup at all. Although outside pellets will be deformed by barrel scrub, your pattern will function very close to the true choke (a completely open barrel with no constriction) of your shotgun. Often used in guns with highly polished or chromed bores, brush wads give you exceptional results. A variation is a wad with a vertical “X” section in the center; these push a pattern much wider than the bore’s marked constriction.
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