guns Simple versioncannon A fuse hole B cannonball
guns
Simple version-cannon • A= fuse hole • B = cannonball bore • Orginally stone • Soon metals for better destruction • C = gunpowder Gunpowder appeared in Europe in 1247 • Cannon introduced in 1327 • Hand cannon in 1364 breech
Matchlock Stock = wooden handles Barrel = metal tube that holds bullet and gunpowder • Lock = ignition mechanism • Light rope • Use trigger to move rope into place
Flintlocks—flint and steel • Flint = very hard rock • Steel = iron alloy • Additives to make it harder • Used to light fires • When flint strikes steel • Flakes off iron • Iron is hot and immediately oxidizes • Hot sparks ignite fuel (gunpowder)
Flintlock – put flint and steel in gun • Hammer = holds and accelerates flint • Mainspring = powers the hammer • Frizzen = holds the steel that flint strikes • Pan = holds small quantity gunpowder waiting for spark • Frizzen spring = holds cover attached to frizzen over pan to make flintlock weatherproof
Flintlock – mechanism to move hammer • Tumbler = holds and releases power of mainspring • Sear and sear spring = engage tumbler and release with trigger
Flintlock – firing 1 - Half-cock hammer 2 – pour measure of gunpowder down barrel 3 – wrap lead ball in cloth or paper and ram down barrel on top of gunpowder 4 – put small amt of gunpowder in pan 5 – snap frizzen in place over pan Half-cock position
Flintlock-firing part 2 • 6 - fully cock hammer • 7 - pull trigger to fire gun When you fire the gun, the flint strikes the frizzen and shaves off iron to create sparks. The hammer's blow also snaps the frizzen back to expose the gunpowder in the pan. The pan's gunpowder ignites, and it flashes through a small hole in the side of the barrel to ignite the gunpowder inside the barrel. The gun fires! Full cock position
Flintlock - rifling • Smooth bore = sides of barrel are smooth • Rifling = engrave groves down inside of barrel in spiral • Typical: one twist in 48 inches • Hard to load without being caught on grooves Rifling improves accuracy imparts spin to the bullet
Percussion Cap—the next step • Replace flint and steel with percussion cap • Mercuric fulminate • Hg(ONC)2 • Made from mercury, nitric acid and alcohol • Shock explosive What the percussion lock does not have is the flint and frizzen. Instead, there is a nipple that accepts the cap, and this nipple contains a tube that leads the flame from the cap down to the main charge of gunpowder in the barrel. The hammer is shaped to strike the cap on the nipple and cover it so the nipple does not get blown off.
Bullet design –internal ballistics • Issues • Form a seal with gun’s bore • (or gases leak instead of propel) • Engage rifling but not • Damage the bore • Distorting the bullet • Without excessive Friction
Bullet design—external ballistics Shape Spherical orientation doesn’t matter Forward center of mass keeps orientation Rotation imparted by rifling Stabilizes bullet Removes (or magnifies) asymmetry
Bullets-materials • Lead (Pb)—a classic • Cheap/available • Simple to fabricate by many forms • Low melting point • Easy to work High density (KE = ½ mv 2) • • soft • Make fabrication easier, but fouls grooves/rifling • Alloy with Sn or Sb to increase hardness • Jacketed Lead • Add hard metal to outside • E. g, Cu/Ni, Cu, steel • Full metal jacket • Completely encase • Soft point/hollow point • Tip not jacketed • Deforming of bullet increases stopping power
Let’s combine: gunpowder, ball and ignition bullet cartridge 1 -- bullet = projectile 2 -- case = holds all parts together 3 – propellant like gunpowder 4 -- the rim, which provides the extractor on the firearm a place to grip the casing to remove it from the chamber once fired 5 – primer = ignites propellant
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