Science and Engineering of Small Arms

Prasanta Kumar Das, Lalit Pratim Das, Dev Pratim Das

• Éditeur: CRC Press
• Année: 2021
• ISBN:
  9781000455090
• Édition: 1
• Sujet: Physical Sciences
• Sous-sujet: Mechanics

This book initiates with the story of the evolution of firearms to enable the reader to appreciate the sequence of the development of firearms. It discusses different classes of small arms, their mechanics, internal and external ballistics. Further, it covers the design idea of barrels and actions, various operating principles and relevant discussion on ammunition and propellants. The principle of quality in the design of the small arms is also elaborated in the desired degree. The book brings out the relevance of modern manufacturing technologies like MIM and various surface treatments, and polymers for enhancement of product quality. To appreciate the sophistication of the architecture, the book presents the anatomical details of a few small arms of reputes.

Provides complete understanding of overall small weapon systems

Explores mechanics and physics of small arms

Discusses proper design, quality control, and manufacturing process selections for a good weapon

Covers common type of weapon failures and catastrophic failure

Includes relevance of manufacturing processes

The book is aimed at professionals and graduate students in Mechanical Design, Armament Design, Gun Design including personnel in the military, paramilitary, police, and all other armed forces and their maintenance crews.

1 A Story of the Evolution of Firearms

DOI: 10.1201/9781003199397-1

The Story of Firearms

The evolution of firearms has been a strenuous journey since the development of gunpowder by the Chinese some thousand years ago. The Chinese could not appreciate the potential of the explosive power to exploit in the making of a weapon suitable for human needs. They mainly used the invention in pyrotechnics for recreational purposes.

FIGURE 1.1 Development of firearms at a glance.

During the 14th century, the knowledge of gunpowder, which was chiefly composed of sulfur, charcoal, and saltpeter mixed in some simple proportion, was passed onto the Europeans, who realized the potential of the explosive power in building up an offensive weapon which can hit the opponents from a distance.

But the problems were manifold, namely,

1. The aggregation of the component of the gunpowder into a single maneuverable entity
2. Identifying a suitable primer to ignite the gunpowder and integrating the same with the main explosive
3. Designing a container which will develop the maximum explosive energy when fired
4. Working out the design of a projectile of optimum aerodynamic shape and mass to transfer adequate kinetic energy at a desirable range with consistent accuracy
5. Developing and understanding the mechanics to ensure the stable trajectory of the projectile
6. Overcoming the constraints of making an accurate device that will convert the chemical energy into pressure energy and propel the projectile imparting predetermined directional properties
7. Want of a firing mechanism that will consistently activate the firearm when needed
8. Evolving a mechanism that will enable to harness rapid and automatic firepower as incorporated in modern-day weapons
9. Development of techniques to produce repeatable parts en-masse, to meet the requirement of production of large numbers of weapons with interchangeability
10. Lastly, the development of a propellant and explosive that deflagrates or detonates in the manners desired to be used as the main charge and primer

The initial solution was to find the design of the explosive container and it was soon realized that a tubular shape device made of strong material would suit the purpose. During the 19th century, progress in science and technology had been steadily taking place.

The steam engine was already invented, and as a result, the techniques of producing a cylindrical container with reasonable accuracy were already in place. The technique was used first to produce the soda-bottle-shaped cast-metal cannons which could use the spherical lead ball projectile and propel it to some 50–75 yards distance.

The canon boring techniques that were derived from the production method of steam-engine cylinders were utilized for producing the cylindrical bore with reasonable accuracy. Thus, it was the canons that emerged as the first kind of firearms to exploit the energy of gunpowder. The weapons in nature were very heavy and not portable and were primarily used for fortification against the enemy.

By this time, an empirical composition of gunpowder consisting of potassium nitrate (saltpeter), charcoal, and sulfur in the approximate proportion of 75:15:10 by weight was established as a prevailing standard. This powder was also known as “black powder”, for which subsequent developments were mainly carried out by Europeans. One of the characteristics of the black powder was that only 50% of the powder burnt properly and the rest was left as a residue. This limited the muzzle velocity of the canons to approximately 1,500–2,000 ft/sec.

The drawback of this explosive was that the burning rate was invariant of the pressure and temperature. In contrast, modern-day propellants based on nitrocellulose burn at a rate almost 100–150 times faster, resulting in the higher development of pressure with efficient burnout. It was however realized by that time that neither the composition nor the grain size of the similar character of explosive is suitable for all types of weapon and the hunt for explosive of refined ballistics went on.

Till the middle of the 15th century, only the large bore cannons prevailed and the need was felt for a smaller weapon which was portable and could be employed for the offensive purpose, and thus the emergence of small arms became apparent on the horizon. The typical method of firing a cannon was very crude. First, some predetermined amount of gunpowder was rammed into the closed-end barrel over which the loosely fitted spherical projectile was placed and through a firing hole at the side of the rear, the weapon was activated. This technique was found to be suitable for use in small arms.

The initial radical changes were brought into the design of firearms through three perceptions:

1. The propelling forces of the gunpowder could be best extracted by firing through the cylindrical hollow tube because the propellant forces on firing had to develop over space and time.
2. The dependence of peak pressure on the inertia of the projectile and the propellant grain size had been only heuristically understood. And the rule of thumb, “The smaller the firearms, the smaller the propellant grain and projectile; and the larger the firearms, the larger the propellant grain and projectiles”, has been applied in the design. This has resulted in a plethora of weapon designs of various sizes and calibers. The issue of caliber and projectile design is a matter of research and investigation even today.
3. The fit of the projectile (spherical ball) had to be snug enough to stop the profuse leakage of propelling gas ahead of the projectile, therefore use a precisely machined cylindrical wrought-iron barrel.
4. To give optimum ballistics (velocity and range), the projectile must be of spherical geometry. This perception, however, has been proved wrong, as can be seen using non-spherical projectile in modern weapons.
5. The issue of managing recoil with the desired projectile energy largely remained in the empirical domain giving birth to several weapon sizes and architecture.

A scheme of the soda-bottle-shaped initial firearms (cannons) is illustrated in Figure 1.2.

FIGURE 1.2 Soda-bottle-shaped initial firearms (cannons).

The Emergence of the First Kind of Portable Arms

The first kind of small arms emerged in the 17th century in the form of a smooth bore muzzleloader using different types of ignition locks (firing mechanism). The development of the locks was a step forward toward the architecture of modern firearms. These muzzleloaders were also popularly known as muskets. An example of a muzzle loader is shown in Figure 1.3.

FIGURE 1.3 Muzzle loader.

The chronological order of the development of the firing mechanism used in the muskets was as below:

• Matchlock
• Wheelock
• Flintlock
• Percussion lock

Brief descriptions of the above firing mechanisms are as follows:

• Matchlock – It was made in the form of an S-shaped arm, called a serpentine. It held a match, and a trigger device used to lower the serpentine, such that the lighted match would fire the priming powder in the pan attached to the side of the barrel. The flash in the pan passed through a small hole in the breech of the gun and ignited the main charge.
• Wheelock – It consisted of a milled edge iron wheel, which was pressed on the fragment of flint to produce a spark on the rotation of the wheel, to ignite the powder. That was very similar to the design of a present-day cigarette lighter.
• Flintlock – In the flintlock mechanism, a spring action caused the frizzen to strike the flint, generating sparks on the gunpowder in the priming pan; the ignited powder, in turn, ignites the main charge in the bore, which pushes the ball forward.
• Percussion lock – Percussion lock used a self-contained, highly sensitive explosive like the modern-day mercury fulminate, or lead styphnate, which when hit sharply detonates and produces a priming flame to ignite the main charge.

In the design of muskets, the designers mainly addressed two issues, namely, the lightweight of the weapon and enhanced firing power. But because of the inevitable relationships between the recoil forces and the mass of the weapon, the designers could not do much either to enhance the firepower or to reduce the size of the weapon.

The typical weapons that were made available in the caliber of 0.69–0.75 inches were about 5.5 ft long, and weighing nearly 20 pounds. They could project fireballs weighing 2 ounces to the targets at 175 yards, that too inaccurately. Also, they required the assistance of two men to fire from a portable rest.

Some unknown genius pondered over the problem of accuracy and heuristically conjectured that spin could probably solve the problem of accuracy. So, it was seen in the 19th century that smoothbore muzzleloaders were gradually being replaced by the breechloading rifles.

Induction of Rifled Barrels

In lethality, smoothbore infantry muskets were relatively inefficient. These used to fire heavy spherical lead balls that could deliver bone-crushing and tissue-destroying blows as they hit the human body. But beyond 75 yards it was inaccurate. At 300 yards, balls from muzzleloaders lost most of their killing power. Well-trained soldiers could load and shoot their muskets five times per minute.

Rifled barrels, in which spiral grooves were cut into the bore, were known to improve accuracy by imparting a spin to the projectile to stabilize it.

The development of the rifled barrel, together with the introduction of percussion lock, gave birth to the architecture of the modern rifle’s predecessors by the end of the 19th century. And the era of the development of modern firearms began.

Mass Production of the Firearms

Several people contributed to the developments of firearms in the last two centuries, but it will be unfair if due credit is not given to the Europeans, who contributed most in the evolution of processes to produce firearms in large numbers and firmly established the need and designed the processes to produce standard parts and standardized patterns.

England took the first steps toward creating a national system of small arms manufacture. An ordnance office decree of 1722 laid the declaration of standard army muskets, known as “Long Land”, that had a 0.75-inch caliber and a 46-inch long barrel.

The first model “Brown Bess” was the popular name given to the Long Land musket.

The U.S. government created national armories at Springfield, Massachusetts, and Harpers Ferry, Virginia, in 1794.

After the introduction of percussion ignition and rifled barrel, which occurred around 1850, the arms manufacturers all over the world started copying the American system of manufacture. This contributed to the ...

Table des matières

• Cover
• Half-Title
• Title
• Copyright
• Dedication
• Contents
• Foreword
• Preface
• Acknowledgments
• About the Authors
• Summary
• Some Useful Conversion Concept and Formulae
• Chapter 1 A Story of the Evolution of Firearms
• Chapter 2 Introduction to Small Arms
• Chapter 3 Theory of Ammunitions
• Chapter 4 Anatomy of Small Arms
• Chapter 5 Basic Design Concepts
• Chapter 6 Quality of Design
• Chapter 7 Special Processes in Small Arms Manufacturing
• Chapter 8 Surface Treatment of Small Arms
• Chapter 9 Common Defects
• Chapter 10 Catastrophic Failure
• Chapter 11 Proof Parameters
• Chapter 12 Interpreting the Technical Specification
• Multiple Choice Questions for Practice
• Index