The bullet is that part of the cartridge that leaves the muzzle of the firearm when it discharges.Bullets were originally lead spheres.These worked satisfactorily with smooth-bore weapons in which the accuracy and long range were not expected.
By the early 19th century however,the superiority of the muzzle-loading rifle over the smooth-bore musket was accepted.These rifled weapons had greater range and considerably more accuracy.The main difficulty however,was in reloading.To make such rifle shoot accurately,the bullet had to fit the bore.This qualification made the gun difficult to load and decreased the rate of fire.The bullet had to be forced down the barrel with a mallet.American rifleman developed a more rapid way of loading their rifles.They used a bullet that was slightly under bore diameter.This bullet was wrapped in a greased patch of fabric and the patch and the spherical bullet were rammed down the barrel together.This step speeded up the rate of loading to some degree but it did not solve the problem.What was needed was to develop a bullet with a diameter less than the bore which would expand to fit the rifling grooves on firing and also would have a better aerodynamic shape than the ball.The solution was the minie bullet,developed by Captain Charles Minie of the french army.It originally consisted of a conical shaped hollow-based lead bullet into whose base an iron wedge was inserted.The bullet was smaller in diameter than the bore and could easily be pushed down the bore.On firing,the gases of combustion would drive the wedge into the base of the bullet,expanding the base of the minie bullet to fit the rifling grooves and to seal the propellant gases behind the bullet.Subsequent research found that the wedge could be eliminated and that the propellant gases working on the hollow base alone were sufficient to flare out the base of the bullet and seal the bore.Soon after the development of the minie bullet ,breech-loading rifled weapons firing metallic cartridges were perfected.Thus,bullets could be made to bore diameter because it was not necessary to force them down the bore during the loading process.
Modern bullets full into two categories:
Lead bullets were traditionally used only in revolvers and .22 rimfire cartridges.Metal-jacketed bullets in automatic pistols and in high velocity rifles.These generalization however are no longer true.
Lead bullets are made out of lead to which antimony and/or tin have been added to increase the hardness of the alloy.These bullets are lubricated with grease or lubricating compound to help prevent lead fouling of the barrel.Lead bullets generally but not inevitably have one or more cannelures or grooves.The Federal Arms Company manufactured a .38 special bullet that had no cannelures.In bullets with cannelures,the cartridge case neck is crimped into one groove with lubricating material placed in the other grooves.When The bullet is assembled in the cartridge case,the cannelures containing the lubricated material may be on the outside and readily visible or beneath the neck of the cartridge case and not visible.
Some lead bullets are covered by an extremely thin coating of copper or copper alloy.This coating which both hardens and lubricates the bullet is called gilding.It is approximately .001 in. in thickness,copper gilding is used extensibly in .22 high velocity rimfire ammunition.Blount industries electro-plates some of its bullets with a thick hard coat of copper such that on initial inspection one believes that one is dealing with a completely jacketed bullet.This coating covers the complete external surface of the bullet including the base.
There are four general configurations of lead bullets.
1. Round nose (a)
2. Wad-cutter (b)
3. Semi-wad-cutter (c)
4. Hollow-point (d)
A round nose lead bullet has a semi-blunt,conical shape and a flat or beveled base.The wad-cutter bullet which resembles a cylinder of lead has a base that may be either beveled or hollow.Wad-cutter bullets are designed primarily for target use.The semi-wad-cutter configuration is that of a truncated cone with a flap tip and a sharp shoulder of bore diameter at the base of the cone.The lead hollow-point bullet has a semi-wad-cutter configuration with a cavity in the nose that is designed to facilitate expansion of the bullet upon impact with the target.
Occasionally,lead bullets with a copper cup crimped to their base may be encountered.This cup is called a "gas check"It protects the bullet base from melting due to the high pressure and temperature of the propellant gases.
Lead bullets ordinarily can not be used in centerfire rifles because the bullet would melt or fragment as it is driven down the barrel at high velocity.The bullet emerging from the barrel would be of bore diameter rather than groove diameter as a result of the lead being stripped from the sides of the bullet.Jacketing is used in high velocity rifles to prevent this fragmenting or melting.Some hand-loaders will load cast bullets of a very hard lead alloy in rifle cartridges.However,the powder loadings are reduced so that muzzle velocity usually does nor exceed 2000 ft/sec.Such cast bullets may or may not have gas checks.
Jacketed ammunition is used in semi-automatic pistols to prevent leading of the action and barrel as well as jam that would result if a large number of lead bullet were fired.These jams are due to the deposit of small fragments of lead on the ramp and in the action as the bullets are stripped from the magazine and propelled up the ramp into the chamber.Hand-loaders sometime use lead bullets in reloading automatic pistol cartridges.
Jacketed bullets have a lead or steel core covered by an outside jacket of gilding metal (copper and zinc),gilding metal-clad steel,copper and nickel or aluminum jackets generally range from .0165 to .030 in. in thickness.Cannelures may be present in the jackets of such bullets to provide a recess into which the mouth of the case may be crimped.
Jacketed bullets may be either full metal-jacketed or partial metal-jacketed.Military ammunition,both rifle and pistol is loaded with full metal-jacketed bullets.Five different types of bullets are in use by the military.The most common is ball ammunition which consists of a bullet with a lead or mild steel core covered by a full metal jacket.Armor-piercing ammunition has a hard steel core.A lead base and point filler may also be present.Tracer bullet consist of a full metal jacket,a lead core in the forward position and tracer composition in the base.In some cartridges the composition is of two types,tracer dim and tracer bright.The tracer dim composition burns first leaving a very dim or faint flame for a distance from the gun,this is followed by tracer bright.Use of the tracer dim composition initially prevents revealing the location of the gun.Incendiary bullets contain an incendiary composition.Armor-piercing incendiary bullets consists of the full metal jacket,a steel core and incendiary material to cause a fire.
Center-fire rifle ammunition used for hunting has always been loaded with partial metal-jacketed bullets.In these bullets,the metal jacket is open at the tip of the bullet to expose the lead core while usually closed at the base.
Until the 1960s,all ammunition intended for automatic pistols was loaded with full metal-jacketed bullets having a lead core.At this time,partial metal-jacketed ammunition was introduced for use in both auto-loading pistols and revolvers.Most handgun ammunition now used by police organizations is partial metal-jacketed.
The two most common forms of partial metal-jacketed ammunition whether for rifles or handguns are the semi-jacketed soft-point and the semi-jacketed hollow-point style.The former style of bullet is most popular for rifles,the latter for handguns.In some rifle ammunition,the lead tip may be covered by a very light secondary jacket,usually of aluminum while others may have an expanding device made of metal or plastic in the tip.The tip of the semi-jacketed soft-point is rounded or pointed in rifles and flattened in a semi-wad-cutter configuration in handguns.A varying degree of lead is exposed depending on the bullet design.The jacket at its junction with the exposed lead core may be scalloped or notched to aid in expansion (mushrooming)In semi-jacketed hollow-point ammunition,the tip of the bullet has a cavity in it.Again,the partial metal jacket may be scalloped or notched to aid expansion or may extend down into the cavity.
Occasionally encountered are full metal-jacketed semi-wad-cutter and wad-cutter handgun bullets used for target shooting.More common are handgun bullets in which the lead core is fully enclosed by a copper jacket.This bullet in conjunction with lead-free primers in the cartridge case is intended for use in indoor firing range and is so designed as to reduce lead pollution of the air.
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