Long story

The long bullet is the successor to the round bullet in the gun field . The advantage of the long bullet over the bullet lies in the higher mass with the same diameter. This increases the cross-sectional load on the projectile, which reduces the braking by the air resistance and increases the penetration power . Long bullets also offer a better seal against the hot gases of the propellant charge when firing , so that no gunshot plasters or other intermediate means are usually necessary.

history

The first long bullet was developed in 1828 by the French captain Delvigne to simplify the loading of rifles. Since this bullet had to be struck into the barrel with a hammer, it was still too unwieldy. In 1848, the French Minié finally developed a long bullet with a hollow bottom. The meaning and purpose of the construction was that the rear of the bullet expands under the pressure of the combustion gases and thus presses into the rifling of the barrel. These so-called expansion projectiles quickly became standard due to their handiness. Despite the comparatively short design with only about 2 to 2½ caliber lengths, the muzzle velocity of the long bullets fell sharply compared to the previously used bullets. Consequently, in order to reduce the cross-sectional load, the caliber was reduced from about 17 to 18 mm previously to about 10 to 11 mm. Around 1890, the development of the low-smoke nitro powder heralded a new era. The greatly increased muzzle energy led to round-head bullets with a length of around 4 calibers. In France, nitro powder was used for the first time with the 8 mm Lebel cartridge. Soon afterwards it became apparent that with such muzzle velocities the round head projectile reached its limits. The further development of the storey was driven forward and in 1898 a new pointed storey was introduced. The superiority of the pointed bullets was evident in the Russo-Japanese War from 1904 to 1905 , when the Japanese army equipped with pointed bullets defeated the tsarist army , which was still equipped with round head bullets. By around 1910, all major armed forces had switched their ammunition to pointed bullets.

Head shapes

Round head bullet

Hemispherical or ogival tips have the advantage that they transfer their energy better in the target. On the other hand, there is a lower muzzle velocity, greater air resistance and thus a smaller range and a more curved flight path. Because of these disadvantages and the Hague Land Warfare Regulations , according to which the projectile effect in the target must be limited to the necessary minimum, the round head projectile could not prevail in military use. It is still popular for hunting ammunition because of its good aiming effect, since the maximum range is not used during hunting.

Another field of application are handguns, as precision and range are limited by other design features.

Flat head bullet

Flat head projectiles are mostly used in weapons with a tubular magazine to prevent the projectile tip of the rear projectile from pressing on the primer of the front cartridge and igniting it. Revolver cartridges are another field of application. Flat-headed bullets are rarely found in self-loaders, as these lead to load jams more often than round-headed or pointed bullets. Like the round head bullets, flat head bullets are popular with hunters because of their great wound effect.

Pointed cone bullet

Pointed cone bullets represent an attempt to combine a relatively good wound effect with good penetration. As tests with the French “Arcane” bullet in caliber 9 mm Parabellum have shown, the bullet meets its requirements and can also be fired by self-loading without any problems.

Pointed bullet

This bullet shape has proven to be the most powerful full-caliber design for bullets on the outside. From a military point of view, it is widely used in long weapons of every caliber and is characterized by very small drag coefficients and good range on flat trajectories. Pointed bullets are optimized primarily in external ballistics, but this also leads to a relatively small wound effect. Militarily, however, this is desirable (Hague Land Warfare Regulations); the ability to penetrate light cover is seen as an advantage here.

optimization

A floor can be optimized for various tasks:

Air resistance
Stability in flight
scattering
effectiveness
Penetrating power

Air resistance

There are basically two starting points for reducing the air resistance: the projectile bow and the rear. Traditionally, it was assumed that the greatest opportunities for optimization were at the bow, since strong shock waves arise at the tip during supersonic flight. However, recent studies have shown that in the supersonic range, the ground suction makes up 50% of the total resistance, while in the subsonic range it is even 80%.

Haack bullet point

The German mathematician Wolfgang Haack was looking for a simplification of fluid dynamics to optimize projectiles. For his calculations he assumed a constant eddy-free flow and limited the consideration to slender floors. Furthermore, he left out the bottom suction, which means that the view as a vortex-free flow is definitely correct. With slender bullets, eddies only occur in the boundary layer , which is already taken into account in the frictional resistance. Haack's efforts resulted in a system of three formulas that can be solved with relatively little effort.

Newtonian bullet point

In Newton's classic flow representation, the rear of the bullet does not experience any force (the impacting particles give the normal component of their momentum to the body and retain the tangential component), which means that the complicated soil suction is omitted from the calculation.

The flow velocity in the direction of the normal to the body is expressed as follows:

${\ displaystyle v_ {n} = v \ cdot \ sin \ delta}$

where represents the tangent angle in the point under consideration. ${\ displaystyle \ delta \! \,}$

Using the law of impulses, this results in the pressure on the body surface:

${\ displaystyle \ Delta p = \ rho \ cdot (v \ cdot \ sin \ delta) ^ {2}}$

The summation of the pressure over the entire surface gives the resistance of the tip. In order to determine a function curve that minimizes the resistance, a slim body must be assumed, just like in Haack's optimization (which is also true). The following approximation is used for this:

${\ displaystyle \ sin \ delta \ approx \ tan \ delta = r '(x)}$

Thus, the tangent gradient of the curve sought can be related to the resistance.

After a long calculation you get the function for an optimal tip, which looks like this:

${\ displaystyle r (x) = {\ frac {d} {2}} \ cdot \ left ({\ frac {x} {h}} \ right) ^ {\ frac {3} {4}}}$

in which: ${\ displaystyle 0 \ leq x \ leq h}$

Based on the flow behavior assumed by Newton, it can be assumed that the optimization of the drag increases with greater speed. The use of this point in practice is made more difficult by the fact that a kink occurs at the transition into the cylindrical part of the projectile. In order to avoid a tear-off edge here, the kink must be rounded off.

comparison

A comparison on an experimental basis can be carried out either in the wind tunnel with enlarged models or in flight with real projectiles. In both cases, however, it must be ensured that the bullets are absolutely identical except for the tips.

Experiments in the wind tunnel with ogival (round), Haack's and Newton's projectile tips showed up to 25% lower wind sensitivity of the pointed projectiles and a much better energy conservation (up to 16% at 300 m and 30% at 500 m). It was also shown that the Haack tip between Mach 1.5 and Mach 3 and the Newton tip above Mach 3 are the most suitable shapes.

Bullet tail

A modern pointed storey that was constructed according to the above criteria

The flow breaks at the stern and creates eddies and a braking suction. The best approach to solving this problem is to create a cone at the stern (also called a torpedo stern) so that the flow follows the projectile longer and the vortex area becomes smaller.

At the moment it is not possible to calculate this exactly, which leaves only test series with tail cones of different lengths and steepness. The results showed that the optimal cone angle is 7 °. As expected, the resistance decreases with increasing cone length, but the optimum (a whole cone) cannot be achieved for practical reasons. Long tail cones greatly increase the range for several reasons. On the one hand, the bullet length must be considered here: anything over five to six calibers can no longer be sufficiently stabilized with twist. If the tail cone is lengthened at the expense of the cylindrical part of the projectile, it can be driven obliquely through the barrel and thus fly less well. A reduction in the tip length leads to greater resistance. In addition, the powder gases generate asymmetrical forces at the rear of the projectile after the muzzle exit, which increase with the length of the cone. The caliber turned out to be the optimal cone length . ${\ displaystyle {\ tfrac {3} {4}}}$

stability

The optimum in terms of flight stability must inevitably go into the type of stabilization. This article deals exclusively with twist stabilization .

From an aerodynamic point of view, it makes sense to increase the cross-sectional load and thus the length of the bullet, but this in turn results in greater radial moments of inertia, which are detrimental to stability. An optimum in this regard is obtained with a projectile length of four to five calibers.

The stability is also influenced by the slenderness of the bullet and thus by the tip height. Experimentally, a tip height of approx. 60% of the floor length has been shown to be ideal.

In order to prevent the bullet from tilting in the barrel, the cylindrical part should be as long as possible, never less than the length of the caliber. On the other hand, the length of the cylindrical part increases the friction in the barrel. In this respect, 1.2 caliber lengths are considered optimal.

scattering

The dispersion in the target is essentially influenced by three components. Probably the least predictable factor in this is the human being: The shooter dispersion is often the greatest contribution. The first technical contribution is weapon dispersion. The precise manufacture of the weapon and good vibration behavior play an important role here in order to keep the spread low.

The third type of scatter, which is mainly discussed here, is bullet scatter. As with many other areas of external ballistics, a good compromise is also required here. For example, the tail cone of modern projectiles is detrimental to precision, but a projectile without a tail cone does not fly far enough to noticeably exploit this advantage. A long cylindrical part increases the stability in the barrel and thus reduces the rolling of the bullet, but it is more susceptible to cross winds.

The only way to optimize a bullet without physical compromises is in manufacturing precision. Some manufacturers of match ammunition (for example in caliber 7.5 × 55 mm Swiss) started to close the jacket at the top instead of beading it at the bottom. This is because the bottom suction contributes much more to the resistance than the bow wave and therefore asymmetries have a stronger effect there. In the sniper sector, full bullets made of brass or bronze alloys are increasingly being used, as these can be turned directly and can therefore be manufactured more precisely. Furthermore, these projectiles are a little lighter, which makes them faster and therefore better suited for firing at moving targets.

effectiveness

Hard goals

In order to improve a projectile's effectiveness against hard targets such as metal armor or the like, the guidelines for aerodynamic optimization can be followed, since here "effectiveness" is primarily defined in terms of high penetration performance.

Basically: a heavy, long projectile (high cross-sectional load) penetrates armor best. In addition, it should be as hard as possible in order to deform as little as possible and to consume its own energy. However, since hard projectiles tend to wear out the barrel of the weapon heavily, sub-caliber projectiles with sabot or projectiles with a hard core and soft jacket are used. Preferred materials for the active part of such projectiles are steel, tungsten or tungsten carbide and depleted uranium.

Soft targets

The optimization of the effectiveness against soft targets corresponds in many respects to the exact opposite of the optimization with regard to air resistance. Great importance is attached to good energy transfer between the projectile and the body tissue of the target. A plug-in shot is favored here, since a penetration still contains energy that does not benefit the target effect. Nevertheless, the energy transfer should not run too fast, otherwise only superficial tissue will be injured and the vital organs will be spared.

Mass stable projectiles

In the case of bullets with stable mass, many tip shapes are used, which can be selected depending on the purpose or preference. As a rule of thumb, the blunt the tip, the better the wound effect, but the worse flight characteristics. The series pointed bullet - cone bullet - truncated cone - semi-wadcutter - wadcutter is intended to serve as an illustration, whereby the flight characteristics decrease and the target effect increases.

In order to avoid the negative effects of blunt projectile heads on the flight characteristics, the deformation projectile was developed. Its best-known shape, the hollow-point bullet, is basically designed like a normal, dimensionally stable bullet (and behaves accordingly in flight), but when it enters a liquid-containing medium in the hole at the bullet tip, a very strong dynamic pressure is created, which the surrounding metal to the outside everts. This means that the diameter can more than double, depending on the design, and thus decisively improve and accelerate the energy transfer. The view that a mandrel inside the cavity has a positive effect on the deformation properties (especially common in the USA) should be referred to as legends. The drilling out of the mandrel of such projectiles did not result in any differences in fire tests.

Other designs of deformation or expansion projectiles have a deformation starter (a tip made of hard plastic or metal) that is pressed into a (usually conical) hole behind it when it hits the target, thus pushing the thin side walls apart. The resulting gaps between the head and the bullet body and the attacking resistance complete the deformation. Such a construction primarily eliminates the often observed failure of hollow point bullets after penetrating light obstacles such as plasterboard walls, wooden panels or thick winter clothing.

In contrast to the reports in some popular media, which put such bullets in the range of dumdum or fragmentation bullets, the deformation is very easy to control and the bullet does not decompose under any circumstances. A higher pain effect in victims has also not been proven.

Dismantling bullets

Disintegration projectiles are designed to either break or release multiple sub-projectiles once they penetrate the target. This can range from soft point bullets with breaking off top two balls inside the (thickened) sheath to fine, rich pressed lead shot in the aluminum sheath. What they all have in common is that by breaking them down, they divide their energy into the fragments and thus reduce the cross-sectional load. For victims who are not fatally hit, such projectiles often carry the risk that either large parts of the tissue are irreparably damaged and / or not all fragments can be found or removed. This represents a long-term health risk, especially with parts containing heavy metals.

literature

Beat Kneubuehl: Projectiles (Volume 1) - Ballistics, accuracy, effectiveness . Motorbuch Verlag, 1998, ISBN 978-3-7276-7119-7 .
Beat Kneubuehl: Projectiles (Volume 2) - ballistics, effectiveness, measurement technology . Motorbuch Verlag, 2004, ISBN 978-3-7276-7145-6 .
Manfred R. Rosenberger: weapons and ammunition used by the police . Motorbuch Verlag 2002, ISBN 3-613-02246-X .

credentials

↑ Info on uranium ammunition

[1] Info on uranium ammunition