Michael Courtney
Member
Effects of Barrel Friction on Muzzle Energy of Handgun Bullets
In a recent experimental study, we developed a method for measuring friction between the bullet and the barrel with a dynamic technique that determines the work done by friction as the bullet traverses the barrel. At relatively low velocities, this friction agrees well with measurements of the force of kinetic and static friction by standard methods.
Preliminary indications are that reducing friction can potentially increase the kinetic energy of handgun bullet by 25% in commonly carried service pistol cartridges such as 9mm, .40 S&W, and .45 ACP. This is important because our pressure wave studies have shown that the ballistic pressure wave represents an important contribution to rapid incapacitation by handgun bullets, and the magnitude of the ballistic pressure wave is proportional to the kinetic energy of the projectile.
Effects of Antimony Content on Jacketed Handgun Bullet Expansion and Fragmentation, and Resulting Magnitude and Location of the Ballistic Pressure Wave
Bullets that rapidly expand and fragment produce a ballistic pressure wave that is increased proportionally to the fraction of mass lost by fragmentation. Rapidly expanding and fragmenting bullets also produce volumes of crushed tissue that can be 2-4 times larger than bullets with moderate expansion and no fragmentation. Both of these factors can significantly decrease the average amount of time it takes for a handgun bullet to incapacitate a violent criminal or terrorist attacker.
Several factors influence the rate of expansion and fragmentation of jacketed handgun bullets. Effects of velocity, pre-cut and pre-stressed bullets, nose design, and jacket composition and design have been extensively studied. Most current bullet designs that expand rapidly and fragment do so in the first two inches of the wound channel, leading to sub-optimal location of fragmentation and pressure-wave effects, since most vital tissue is located deeper than 2 inches. It would be more effective to delay rapid expansion and fragmentation until deeper in the wound channel to optimally locate pressure wave effects nearer to vital tissues.
Preliminary research indicates that hardening the frontal section of a copper jacketed lead hollow-point bullet can delay the desired rapid expansion and fragmentation until the bullet has penetrated to a more optimum depth for creating more severe wounding and larger pressure wave that result from rapid expansion and fragmentation. The goal of this project is to quantify how hardening lead by the introduction of antimony can delay expansion to a more optimal depth.
Flattening the Pressure Curve to Increase Bullet Energy
An important limiting factor in handgun bullet effectiveness is the kinetic energy that can be delivered from a handgun-sized projectile launcher. The limiting factor for kinetic energy of handgun bullets is the pressure that can be contained in the chamber and barrel of the gun. Steel strength and bulk determine the maximum pressure that a chamber and barrel can contain. However, the kinetic energy of the bullet depends on the average pressure as the expanding gasses propel the bullet down the barrel. Therefore, flattening the pressure curve, by raising the average pressure closer to the peak pressure, is a viable approach to increasing handgun bullet effectiveness.
The chemistry of smokeless gun powders has changed very little over the last 100 years with burn rates controlled by changing the size and shape of the nitrocellulose propellants, the addition of burn rate retardants, and also by the use of some double-base propellants that include nitroglycerine. Combined with reducing barrel friction, achieving significantly flatter pressure curves can potentially double the kinetic energy of handgun bullets without increasing the strength, cost, or bulk of the handguns themselves.
Reducing barrel friction is an important first step, not just because friction robs kinetic energy, but also because friction in current bullet/barrel designs is unpredictable, and when it is unexpectedly high, it leads to a pressure-induced increase in burn rate with current propellants. This can lead to pressure spiking which increases the peak to average ratio of the pressure curve.
Beyond reducing barrel friction, several chemical approaches are possible to flattening the pressure curve. These include using propellants that are less progressive in their burn characteristics, including endothermic components in the propellant so that the propellant itself can absorb energy above a certain pressure or temperature threshold, and including propellants with many degrees of freedom so that the early expansion of the unburned propellant exerts greater cooling on the burning propellant and flattens the pressure curve.
The combination of reducing barrel friction and keeping the barrel pressure closer to the maximum can increase bullet energy by at least 100% without increasing the size or bulk of service caliber handguns.
Michael Courtney
In a recent experimental study, we developed a method for measuring friction between the bullet and the barrel with a dynamic technique that determines the work done by friction as the bullet traverses the barrel. At relatively low velocities, this friction agrees well with measurements of the force of kinetic and static friction by standard methods.
Preliminary indications are that reducing friction can potentially increase the kinetic energy of handgun bullet by 25% in commonly carried service pistol cartridges such as 9mm, .40 S&W, and .45 ACP. This is important because our pressure wave studies have shown that the ballistic pressure wave represents an important contribution to rapid incapacitation by handgun bullets, and the magnitude of the ballistic pressure wave is proportional to the kinetic energy of the projectile.
Effects of Antimony Content on Jacketed Handgun Bullet Expansion and Fragmentation, and Resulting Magnitude and Location of the Ballistic Pressure Wave
Bullets that rapidly expand and fragment produce a ballistic pressure wave that is increased proportionally to the fraction of mass lost by fragmentation. Rapidly expanding and fragmenting bullets also produce volumes of crushed tissue that can be 2-4 times larger than bullets with moderate expansion and no fragmentation. Both of these factors can significantly decrease the average amount of time it takes for a handgun bullet to incapacitate a violent criminal or terrorist attacker.
Several factors influence the rate of expansion and fragmentation of jacketed handgun bullets. Effects of velocity, pre-cut and pre-stressed bullets, nose design, and jacket composition and design have been extensively studied. Most current bullet designs that expand rapidly and fragment do so in the first two inches of the wound channel, leading to sub-optimal location of fragmentation and pressure-wave effects, since most vital tissue is located deeper than 2 inches. It would be more effective to delay rapid expansion and fragmentation until deeper in the wound channel to optimally locate pressure wave effects nearer to vital tissues.
Preliminary research indicates that hardening the frontal section of a copper jacketed lead hollow-point bullet can delay the desired rapid expansion and fragmentation until the bullet has penetrated to a more optimum depth for creating more severe wounding and larger pressure wave that result from rapid expansion and fragmentation. The goal of this project is to quantify how hardening lead by the introduction of antimony can delay expansion to a more optimal depth.
Flattening the Pressure Curve to Increase Bullet Energy
An important limiting factor in handgun bullet effectiveness is the kinetic energy that can be delivered from a handgun-sized projectile launcher. The limiting factor for kinetic energy of handgun bullets is the pressure that can be contained in the chamber and barrel of the gun. Steel strength and bulk determine the maximum pressure that a chamber and barrel can contain. However, the kinetic energy of the bullet depends on the average pressure as the expanding gasses propel the bullet down the barrel. Therefore, flattening the pressure curve, by raising the average pressure closer to the peak pressure, is a viable approach to increasing handgun bullet effectiveness.
The chemistry of smokeless gun powders has changed very little over the last 100 years with burn rates controlled by changing the size and shape of the nitrocellulose propellants, the addition of burn rate retardants, and also by the use of some double-base propellants that include nitroglycerine. Combined with reducing barrel friction, achieving significantly flatter pressure curves can potentially double the kinetic energy of handgun bullets without increasing the strength, cost, or bulk of the handguns themselves.
Reducing barrel friction is an important first step, not just because friction robs kinetic energy, but also because friction in current bullet/barrel designs is unpredictable, and when it is unexpectedly high, it leads to a pressure-induced increase in burn rate with current propellants. This can lead to pressure spiking which increases the peak to average ratio of the pressure curve.
Beyond reducing barrel friction, several chemical approaches are possible to flattening the pressure curve. These include using propellants that are less progressive in their burn characteristics, including endothermic components in the propellant so that the propellant itself can absorb energy above a certain pressure or temperature threshold, and including propellants with many degrees of freedom so that the early expansion of the unburned propellant exerts greater cooling on the burning propellant and flattens the pressure curve.
The combination of reducing barrel friction and keeping the barrel pressure closer to the maximum can increase bullet energy by at least 100% without increasing the size or bulk of service caliber handguns.
Michael Courtney