The history of bullets far predates the history of firearms. Originally, bullets were metallic or stone balls used in a sling as a weapon and for hunting.
Eventually as firearms were developed, these same items were placed in front of an explosive charge of gun powder at the end of a closed tube. As firearm became more technologically advanced, from 1500 to 1800, bullets changed very little. They remained simple round (spherical) lead balls, called rounds, differing only in their diameter.
The development of the hand coverings and matchlock arquebus brought about the use of cast lead balls as projectiles. "Bullet" is derived from the French word boulette which roughly means little ball. The original musket bullet was a spherical lead ball smaller than the bore, wrapped in a loosely-fitted paper patch which served to hold the bullet in the barrel firmly upon the powder. (Bullets that were not firmly upon the powder upon firing risked causing the barrel to explode, with the condition known as a short start.) The loading of muskets was, therefore, easy with the old smooth-bore Brown Bess and similar military muskets. The original muzzle-loading rifle, on the other hand, with a more closely fitting ball to take the rifling grooves, was more difficult to load, particularly when the bore of the barrel was fouled from previous firings. For this reason, early rifles were not generally used for military purposes.
The first half of the nineteenth century saw a distinct change in the shape and function of the bullet. In 1826, Delvigne, a French infantry officer, invented a breech with abrupt shoulders on which a spherical bullet was rammed down until it caught the rifling grooves. Delvigne's method, however, deformed the bullet and was inaccurate.
Square bullets were used in one version of the Puckle gun.
Bullet designs have to solve two primary problems. They must first form a seal with the gun's bore. If a strong seal is not achieved, gas from the propellant charge leaks past the bullet, reducing efficiency. The bullet must also engage the rifling without damaging the gun's bore. Bullets must have a surface which will form this seal without causing excessive friction. These interactions between bullet and bore are termed internal ballistics. Bullets must be produced to a high standard, as surface imperfections can affect firing accuracy.
The physics affecting the bullet once it leaves the barrel, is termed external ballistics. The primary factors affecting the aerodynamics of a bullet in flight are the bullet's shape and the rotation imparted by the rifling of the gun barrel. Rotational forces stabilize the bullet gyroscopically as well as aerodynamically. Any asymmetry in the bullet is largely canceled as it spins. With smooth-bore firearms, a spherical shape was optimum because no matter how it was oriented, it presented a uniform front. These unstable bullets tumbled erratically and provided only moderate accuracy, however the aerodynamic shape changed little for centuries. Generally, bullet shapes are a compromise between aerodynamics, interior ballistic necessities, and terminal ballistics requirements. Another method of stabilization is for the center of mass of the bullet to be as far forward as is practical, which is how the Minié ball and the shuttlecock are designed. This allows the bullet to fly front-forward by means of aerodynamics.
See Terminal ballistics and/or Stopping power for an overview of how bullet design affects what happens when a bullet impacts with an object. The outcome of the impact is determined by the composition and density of the target material, the angle of incidence, and the velocity and physical characteristics of the bullet itself. Bullets are generally designed to penetrate, deform, and/or break apart. For a given material and bullet, the strike velocity is the primary factor determining which outcome is achieved.
Bullet shapes are many and varied, and an array of them can be found in any reloading manual that sells bullet moulds. Mould manufacturers such as RCBS, Paul Jones Moulds, and David Mos offer many different calibers and designs. With a mould, bullets can be made at home for reloading one's own ammunition, where local laws allow. Hand-casting, however, is only time- and cost-effective for solid lead bullets. Cast and jacketed bullets are also commercially available from numerous manufacturers for hand loading and are much more convenient than casting bullets from bulk lead.
WANT TO BUY BULLET FOR YOUR COLLECTION? GO HERE DETVIETCRAFT
WANT TO BUY BULLET FOR YOUR COLLECTION? GO HERE DETVIETCRAFT
No comments:
Post a Comment