Classic lead slugs
Lead as a bullet material has been known since the very beginning of firearms. The specific weight of lead (11.34 g/cm3) makes it one of the heaviest widely available metals. Therefore, for centuries till nowadays, lead has been the main material used for bullet and slug making. Lead is a soft and heavy metal, easy to melt, cast and press. Thanks to its large specific weight, the size of lead slugs is relatively small. The good deformation capability of lead is especially suitable for smooth bore weapon slug production and shooting them through barrels with relatively thin walls. When passing through the barrel under propellant gas pressure, a lead slug becomes deformed, centers itself and firmly seals the barrel. Meanwhile, when hitting the target, lead slugs become deformed again, increase their size and effectively transfer their kinetic energy into an animal' body.
Nevertheless, lead slugs have their shortcomings. When a lead slug receives the propellant gas pressure impact in the first moment of a shot, its deformation is not always regular. As a result, an irregularly deformed slug body during its flight tends to deviate from the initially assumed placement. If a lead slug hits an obstacle, it becomes deformed further, and looses its symmetry and initial flight path – this effect is called ricocheting. Because of their low velocity, lead slugs have an inexplicit expansion effect. It is mainly noticed when lead slugs hit large bones deep in the body. In cases when lead slugs disintegrate after hitting bones, small lead fragments are impossible to find and make their way into consumed food and the environment as heavy metal pollutants. Lead slugs often create a tough layer of lead fouling on barrel walls, thus affecting ballistic characteristics of every next shot.
New materials in everyday life
Over time, new materials emerge in everyday life. Polymers have found their use in making plastic shell cases and shot containers, thus giving new ballistic characteristics to shotgun ammunition and making shotshell loading processes easier and more productive. The polymer elasticity allows shooting hard metal parts encased into plastic containers through barrels with no concern. Once an innovation, plastic ammunition parts are widely used nowadays. At the moment, steel slugs in polymer casings have been tested for more than twenty years and now are not new in the Baltic region. In the future, it is possible that steel slugs will eventually replace the environmentally unfriendly lead slugs and become quite common.
Slug body made of steel!
Steel (specific weight 7.8 g/cm3) is a material usually regarded as unusable for shotgun slug making because of its characteristics. Nevertheless, its high resistance against deformation in the first moment of firing allows designing a very aerodynamically advantageous slug shape. A narrow bar in the slug’s middle part and cone in the rear divide its mass in two parts. During the shot, a slug’s frontal part acts as an imaginary pivoting joint, followed by the rear part with a stabilizing cone and plastic wad. The ideal mass distribution along with high aerodynamic pressure on lateral parts of the rear cone and wad stabilizes the slug during its flight. Unlike classic slugs, a slug made like this is impossible to knock over during the flight. Usually, D Dupleks slugs fly and hit the target with the nose forward.
The hardness of steel slugs matches the barrel material or comes very close to it. That creates a range of technical problems. Casting and pressing slugs of sophisticated shape without complex finishing is quite difficult and labor-consuming. The most reasonable technique is steel slug body lathe-machining with automated machinery. This method ensures high accuracy, despite being slow, sophisticated, and demanding large high quality and energy consuming machines. An enormous advantage of the lathe-machining method is the creation of non-deformable steel slug shape, centered along its longitudinal axis. Another solution found by D Dupleks – encasing the steel slug body in a melted polymer under pressure – proved itself to be fully technological and safe. When shooting such slugs through barrels with different chokes, highly accurate results of slug placement were obtained.
Steel through barrel - safely
Monolit 28, Monolit 32, Dupo 28, Rossa 32 and Hexolit 32 slugs have polyethylene rings in their frontal part and stabilizing wads in the rear part, which ensure flawless shotshell case crimp opening and centering the slug body within the barrel. The diameter of the steel slug body for every gauge is calculated in such a way to ensure fully safe slug passage through the narrowest possible standard shotgun choke. Also, length dimensions of slugs are designed to be no less than the diameter of the barrel. This eliminates the possibility of the slug to twist in an acute angle and damage the internal barrel surface during the shot.
The polymer ring on the slug’s frontal part is pressed onto the steel body under high pressure with great accuracy. Thus, it is capable of resisting heavy loads during the first moments after firing, as well as ensuring perfect slug centering and its safe passage through the barrel. The forces acting during a shot facilitate pressing the plastic parts into the slug body. Polyethylene parts pressed onto steel body have better sliding characteristics; they do not create fouling on the metal surface and effectively prevent damage.
During several years, almost 7500 shots were fired through the D Dupleks ballistic data test barrel (internal diameter 18.4 mm, 1 mm full choke narrowing). This barrel looks like new, it does not have any flaws or damage.
Monolit slug series
The Monolit slug series design is distinctive with its balancing cone which ensures slug self-centering during flight. When exiting the barrel, a powerful propellant gas stream hits the rear part of the slug, often knocking it off balance and it's initial flight path. In such cases, thanks to the balancing cone and large lateral surface of the plastic wad, Monolit slugs quickly regain their balance. Self-stabilization during the flight is the most distinctive characteristic of these slugs. They simply cannot fly sideways.
Aerodynamics versus power of impact
During many ballistic experiments with various slug designs, a lot of attention was paid to effective kinetic energy transfer at the moment of impact. Thin-diameter slugs with a pointed forepart design distinctively tended to punch through an animal’s body and carry away a large share of their kinetic energy. Thin slugs have little aerodynamic resistance; however, this energy saved in flight could not be effectively transferred into an animal’s body due to the small frontal surface of the slug. To ensure effective kinetic energy transfer, the D Dupleks Monolit slug series has been designed with a straight, flat frontal surface. Such slugs loose their aerodynamic characteristics somewhat; however, a powerful impact effect with a large flat forefront surface is achieved.
D Dupleks slugs can be effectively used within distances up to 100 m; nevertheless, successful shots often have been made at quite longer distances. The experience and statistical data on long-distance shots in hunting, summarized by D Dupleks, confirms the following – an increased aerodynamic resistance of a flat frontal surface cannot negatively affect a significantly powerful impact effect, even at 120-140 m distances, which are quite long for these slugs. Despite the fact that increased aerodynamic resistance on flat frontal surfaces is unquestionable, ammunition tests showed that the impact provided by a flat forefront surface is effective at incredibly long distances. The explanation is simple. Even at long distances, in the moment of impact, a large forefront surface ensures effective transfer of all kinetic energy much better than thin-diameter bullets. For accurate, successful long-distance shooting, other factors prevail over small frontal aerodynamic resistance – those are initial slug velocity and weapon recoil characteristics, determining the slug exit angle regarding the point of weapon support.
Expanding slug series
Expansive effect from the first moment of hit
The design of all D Dupleks expanding slugs is unique with their inward cone in the slug's forefront part. This ensures immediate slug expansion at the first moment of impact. No matter if the slug has hit a large moose or small fox – its forefront expands instantly. The slug forefront design, dimensions and material characteristics are adjusted together in such a way that the slug expansion directly depends on target density. The density of animal skin and muscles underneath is very close to the density of water. On entering such an environment, D Dupleks expanding slugs open up instantly. Hitting a target with water density creates large pressure in a slug’s forepart cone, immediately expanding leaflets, until they are stopped by the supporting shoulder.
Paradoxically, if the slug hits wood, steel plate, dense grass, bushes or tree branches, its forefront does not expand at all, or expands only partially. The slug forefront is designed to be a rigid metal construction, encased by polymer. On hitting hard targets, it retains its initial shape. The inward cone is filled by hard material punched out of the target, which in turn is rigid itself. Therefore, the slug does not expand and retains its initial shape well.
The blossoming slugs
The slugs of the D Dupleks expanding series have various expansion diameters. When hitting an animal body, slug forefront leaflets instantly open up and butt against the supporting shoulder. In such a way, a strong and rigid construction is formed. The slug forefront part increases its diameter from 18.4 mm to 27-36 mm and effectively transfers all of its kinetic energy into the animal body on impact. Usually, only a large entrance hole is observed, but no exit hole. Thanks to the slug’s large forefront area, all its energy stays in the animal body.
If the shot is made from a distance less than 20 m, at the moment of impact, slug’s kinetic energy exceeds metal strength. During hydrodynamic impact with a large expansion area, the slug forefront metal cannot resist the overload and splits apart. Thus, a regular splinter cone of hexagonal shape is formed, with the remaining part of the slug in the middle. At first, the slug makes an impact with its expanded forefront area, and then impact is continued by the splinter cone and remaining part of slug, damaging bones, soft tissue and various vital organs on their way. On hitting an animal body with 25-30 cm in thickness, the splinter cone diameter on the opposite side of the body is 25-30 cm. Three splinters travel upwards. If an imperfect shot is placed in the abdomen, those three splinters usually hit the spine or nerves nearby, paralyzing the rear part of the animal. The fragmented slug parts usually do not exit the body, fully transferring their energy.
Significantly, the D Dupleks expanding slug series practically shows the effect that can be hardly seen when shooting other slugs or bullets with a smaller expansion diameter. On hitting different parts of an animal body, D Dupleks expanding slugs perform differently. It turns out that the frontal part of the animal, or its ribcage, is not so dense as the rear part, or abdomen, which is filled by various liquids. Here, D Dupleks expanding slug peculiarities can be observed fully.
On hitting the ribcage, the slug expands instantly, retains initial expansion shape and performs an impact all the way to elastic skin on the opposite side. Such slugs usually do not exit the body. Their large expansion area facilitates complete kinetic energy transfer. On hitting the abdomen, the slug punches a large entrance hole with a 3-3.5 cm in diameter, then opens up and impacts powerfully with its expansion area; after that, in most cases slug fragmenting and splinter cone impact is observed.
If the shot is made from a short distance (up to 20-35 m), in almost all cases, slug fragmentation is noticed. When shooting at a 35-100 m distance, the effects of an expanding slug hit are different, depending on hit placement. On a ribcage hit, slugs expand and retain their shape; on an abdomen hit, they expand and split apart. If the abdomen is hit from a longer distance (above 100 m), it is possible for a slug to expand and retain its shape. This is explained in the following way – slug energy is maximal when exiting the barrel, but consequently reduces over distance. Thus, forces reducing the expanded slug forefront become smaller. Both the first and second slug impact effect is significantly superior to one caused by conventional classic shotgun slugs.
Hydrodynamic shockwave – unique characteristics of expanding slug series
The D Dupleks expanding slug series have another powerful hit effect, un-common conventional shotgun slugs. The expanding slugs do not create large blood effusions in the location of impact which usually damage the meat. Despite large slug entrance holes and tissue perforations caused by splinters, blood effusions in those areas are small and inexplicit, or completely absent.
In the first moment of impact, the slug expands to the maximum diameter and punches a large entrance hole. In the next moment, increased forepart of slug causes a powerful hydrodynamic shockwave inside the animal body. It instantly affects animal’s respiratory, circulatory and neural systems. The three main vital systems are crushed all at once. Blood circulation and vital processes cease instantly.
For almost ten years, D Dupleks have summarized statistics on expanding slug impact effects in photo and video image forms. Both photo images and video clips clearly display the fact that blood effusions underneath the skin in slug hit locations are distinctively small. This indicates that the hydrodynamic shockwave has stopped blood circulation at the moment of impact. In a ribcage hit, intestine fragments and blood are clearly visible, blown out by high air pressure through the slug entrance hole. In an abdomen hit, the high air pressure usually blows out some portion of intestines through the entrance hole, about 0.2-2 kg in weight.
Thus, expanding slugs perform several stopping effects all at once – combined impact, large entrance hole, slug fragmentation along with splinter cone damage, and powerful shockwave. Each of those effects is sufficient enough to bag the animal. However, a hydrodynamic shockwave inside animal body is the most effective.