One of the ammunition design constraints limiting the overall performance level of firearms is its barrel overheating, particularly for weapons firing high-energy ammunition at the muzzle at high firing rates.
Indeed, the operating principle of a firearm consists in propelling a projectile by the pressure of hot gases generated by the combustion of a propellant charge. This means that some of the thermal energy present in the propellant gases is lost through the heat transferred to the barrel’s inner wall, causing it to heat up significantly.Any shortcomings in the thermal management of a weapon result, at best, in a deterioration of the barrel’s service life (loss of accuracy due to the advance of the rifling in the barrel), and at worst, in a deterioration of the weapon’s safety (risk of cook-off, explosion of the barrel under mechanical stress during firing).

State of the Art

To compensate for the degradation of the barrel’s mechanical performance as it rises in temperature, a weapon designer must integrate passive or active cooling solutions (rapidly replaceable heavy barrel, cooling fins, heat sink, liquid cooling, etc.), or failing that, limit the power of usable ammunition or the acceptable firing rate.

Proposed solution

To reduce the thermal load on the barrel directly, without reducing the performance of the ammunition, the solution is based on the formation of a protective film on the inner wall of the barrel, as the projectile passes through, eliminated by the propellant gases. In this way, direct contact between the propellant gases and the barrel is delayed at least as long as it takes for the film to degrade, which means that the inner wall of the barrel is only subjected to significant heat transfer after a period of time that allows the temperature of the gases to fall as they expand in the barrel.

This protective film is formed by the transfer of material from a sabot surrounding the projectile, deposited on the barrel wall by erosion as the projectile passes through the barrel. To force and control the rate of degradation of the sabot, and thus control the thickness of the protective film, the barrel is tapered to reduce its internal diameter as the projectile progresses through the barrel, to a minimum determined by the diameter of the projectile.

To avoid excessive clogging of the barrel and facilitate evacuation of the protective film during each shot, the material used to manufacture the sabot must have at least one of the following properties:

A melting or sublimation temperature lower than the temperature reached by the combustion gases present in the conical section of the gun during firing.
A chemical composition complementary to that of the propellant gases, so that contact between the two is conducive to a chemical reaction whose products are in the gaseous state.
Contain a high proportion of propellant with a low combustion rate and relatively low combustion temperature.

Calculated performance

The implementation of this innovation makes it possible to achieve a level of performance in terms of projectile velocity at the muzzle of the barrel substantially higher than that obtained by a standard barrel of the same length, and potentially of the same order as that of an under-calibrated projectile using an aluminum sabot in a straight barrel with the initial diameter of the tapered barrel.

L’article Reducing the thermal load on the barrel: FR 22 04908 est apparu en premier sur Initial Velocity Lab.

The very operating principle of a firearm is based on the thrust of the projectile by a pressurized gas. This gas is obtained by the combustion of a propellant charge inside the closed barrel, at the rear by a breech, while the seal between the barrel and the projectile is maintained either by direct contact between the barrel and the projectile, or by means of a belt, or through a sabot in the case of sub-caliber ammunition.

The performance of a weapon is often equated with the maximum kinetic energy given to the projectile as it leaves the barrel. Regardless of the projectile’s mass or desired muzzle velocity, to maximize the weapon’s performance, the pressure at the projectile’s base must be as high as possible for as long as possible, which implies maximum pressure throughout the barrel. Thus, increasing the performance of a weapon necessarily means subjecting the barrel to greater mechanical stress along its entire length.

State of the Art

The maximum operating pressure of a weapon is a parameter defined during ammunition design primarily by the strength of the standard barrel to be used. During this process, a number of parameters are fixed more or less definitively in the form of standards, so as to guarantee interoperability between weapons and ammunition of the same caliber, in complete safety for the operator.
In the case of high muzzle velocity firearms, the thickness of the barrel wall at the breech is often greater than the internal diameter of the barrel, which means that the maximum working pressure is directly linked to the elastic limit of the barrel material. Thus, an ammunition designer has only a limited number of solutions to improve the ammunition performance :

Increase the duration of maximum thrust: by lengthening the barrel and increasing the volume of the case to increase the propellant charge, but above all by adopting much more complex powder
geometries so that maximum pressure is maintained for longer despite the increased volume available for the propellant gases as the projectile advances through the barrel.
Increase the bearing surface of this maximum pressure by increasing the caliber of the weapon and adopting a sub-calibration device.

While the quality of the steels used to manufacture firearms has always been a driving force in improving the performance of these weapons, it has to be admitted that a performance peak was reached when the steels developed for nuclear programs were made available to the arms industry in the 1970s-1980s.

Proposed solution

To reduce the stress on the gun during firing, it is imperative to transform the energy distribution within the gun, propellant gas and projectile assembly, so as to reduce the proportion of thermal energy from the propellant gases within the gun, which is responsible for the pressure on the gun walls. The proposed solution consists in maximizing the velocity of the gases in the barrel axis as early as possible in the barrel, so as to transform part of the thermal energy of the propulsion gases into kinetic energy.
To achieve this, it is necessary to separate a combustion chamber, in which the high pressure required to maintain combustion prevails, from the barrel, in which the propellant gases push against the projectile, mainly the projectile itself. The separator consists of a Laval nozzle which, once primed, allows the propellant gases to undergo a significant expansion before being recompressed behind the projectile.

This solution offers the following advantages:
Once the nozzle is primed, the pressure distribution in the barrel passes through a minimum at the nozzle outlet and a progressive compression along the barrel, so that the maximum pressure in the barrel is at the projectile base, as long as the nozzle is primed.
The gases leaving the nozzle, once primed, have a higher velocity than that of the projectile, making propulsion of high muzzle velocity projectiles more efficient.
A large proportion of the solid propellant charge can be trapped in the combustion chamber, whose volume remains constant during firing. This simplifies the powder geometry required to achieve
constant pressure over time, since it is no longer necessary to compensate for an increase in volume by increasing the combustion surface. It also minimizes unburnt emissions, since the pressure in the combustion chamber is fixed by the cross-section of the nozzle throat.

Calculated Performance

In addition to reducing the pressure applied to the barrel walls, the implementation of this innovation translates in theoretical results into a second peak in projectile acceleration at muzzle initiation. This implies a more efficient use of the entire barrel, and therefore a higher muzzle velocity for the same barrel length.

L’article Reducing mechanical stress on the barrel: FR 22 04909 est apparu en premier sur Initial Velocity Lab.

Production methods for ammunition intended for military use (particularly for small-caliber weapons) have not evolved significantly since the standardization of 5.56 x 45 mm ammunition in the mid-1960s.
This is due to the close relationship between the case production method and the performance obtained, such as maximum admissible pressure, or the mechanical strength of the case during the extraction of the fired case from the chamber.
However, production methods in other industries have evolved considerably, so much so that the processes used to manufacture ammunition with monolithic metal casings have been replaced by others that consume fewer resources, energy and, above all, manpower. As a result, the industries needed to produce ammunition using these processes and located in Western countries have lost a lot in competitiveness, leading to relocation and a loss of sovereignty over ammunition supply chains.

State of the Art

The production of ammunition case for small arms (5.56 mm and 7.62 mm calibers, but also .50) has remained static since the late 1960s, and is itself the result of particularly conservative approaches in technological terms. Indeed, the manufacturing process involves the use of mechanical presses to produce the case (as well as the projectile jacket) by cold-forging, interspersed with cleaning operations and heat treatments to avoid the creation of stresses that would cause tearing, either during manufacture, or when the ammunition is used.
As demonstrated by developments in the field of medium and large-caliber weapons, the non-reversible modernization of weapons and ammunition systems, when it involves a change of caliber, is the ideal circumstance for drastic update in the ammunition production methods.
In this respect, the implementation of the innovation protected by patent FR 22 04909 of separation between the chamber and the barrel can be considered sufficiently complex on an industrial scale to justify a complete overhaul of ammunition production methods. This is all the more true since, in order to maximize the duration of secondary thrust, it is necessary to maximize propellant retention in the chamber during firing, by using powder grains with dimensions greater than the cross-section of the neck.

Proposed Solution

To enable propellant filling of the combustion chamber of a munition implementing the innovation protected by patent FR 22 04909, it is useful to make the case in several parts, which are assembled after loading with propellant powder. In order to guarantee the solidity of the case body assembly, particularly when it is removed after firing, a third part can be used to lock the assembly together, preventing the base and insert, in which the nozzle separating the combustion chamber from the barrel, from being disassembled.

The ideal material for the base of the cartridge case is lacquered steel, to take advantage of its increased strength compared with that of the brass usually used in older cartridges, in order to maximize chamber pressure in complete safety. The insert in which the nozzle is formed, enabling propulsion gases to pass through the gun at supersonic velocity, can be made from substantially lighter materials, such as certain plastics, provided they are resistant to thermal stress. For this purpose, a material such as ceramic can be used, either in the form of a composite with ceramic in the form of glass microspheres embedded in a polymer matrix, or in the form of a surface treatment on the surfaces exposed to the propulsion gases.

Two architectures are preferred:
An architecture with a long base and a short insert, where the combustion chamber is formed in the base. In this configuration, the chamber is closed by crimping the base onto the insert. An external locking device can be fitted.
An architecture with a long insert and a short base, where the combustion chamber is formed in the insert. In this configuration, it is preferable to internally lock the assembly by means of a spacer
passing through the channel between the insert and the combustion chamber.

L’article Method of assembling ammunition with separate combustion chamber : FR 24 11345 est apparu en premier sur Initial Velocity Lab.

Compromise between the need for increased terminal performance, compatibility with firing regimes linked to saturation, ensuring mass availability of weapons and ammunition required for sovereignty.

Solutions :

Combining the innovations presented in patents FR 22 04908 and FR 22 04909, the complementary nature of which enables the creation of a solution offering significant gains in terminal performance without sacrificing the versatility of small-caliber individual weapons, thanks to the cumulative improvements in the management of thermal and mechanical stresses on the barrel.

The implementation

of a new weapon and ammunition pairing is also an opportunity to modernize production resources by adopting global manufacturing processes in line with the industrial fabric of developed countries, as demonstrated by the innovation protected by patent FR 24 11345.

Commercial information

Patents: FR 22 04908, FR 22 04909 and FR 24 11345
Protected countries : Europe + United States + Israel + South Korea

L’article Individual arming est apparu en premier sur Initial Velocity Lab.

Need to upgrade the terminal performance of earlier-generation weapons systems that have lost their relevance, in order to rapidly give the armed forces back mass, and diplomacy leverage, through the provision of modernized equipment.

Solutions :

This can be achieved by expanding the range of anti-tank ammunition available, backward-compatible with legacy 105 mm caliber weapon systems. The adoption of a separated chamber ammunition, based on the innovation described in the patent FR 22 04909, should deliver the terminal performance gains needed to bring Leopard 1, AMX 30 and first-generation Abrams tanks back to the forefront in the context of a high-intensity conflict. The implementation of a new ammunition is also an opportunity to modernize production resources by adopting global manufacturing processes in phase with the industrial fabric of developed countries, as demonstrated by the innovation protected by patent FR 24 11345, while guaranteeing that newly produced ammunition meets the MURAT / STANAG 4439 safety standard.

Commercial information :

Patents: FR 22 04909 and FR 24 11345
Protected countries : Europe + United States + Israel + South Korea

L’article “Legacy” large caliber weapons est apparu en premier sur Initial Velocity Lab.