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CRIMINAL INVESTIGATIONS

CRIMINAL INVESTIGATIONS. AMMUNITION/ BALLISTICS. AMMUNITION. Cartridge Structure Cartridge Case Primer Head Propellant Bullet Blanks- No Bullet. Metal Jacket. Ammunition. AMMUNITION. Cartridge Cases Made of Brass 30% Copper 30% Zinc Aluminum Brass, Plastic and Paper for shotguns.

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CRIMINAL INVESTIGATIONS

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  1. CRIMINAL INVESTIGATIONS AMMUNITION/ BALLISTICS

  2. AMMUNITION • Cartridge Structure • Cartridge Case • Primer • Head • Propellant • Bullet • Blanks- No Bullet

  3. Metal Jacket

  4. Ammunition

  5. AMMUNITION • Cartridge Cases • Made of Brass • 30% Copper • 30% Zinc • Aluminum • Brass, Plastic and Paper for shotguns

  6. AMMUNITION • Function of Cartridge • Expand and seal chamber • Increase Gas Pressure • Press the case up against barrel • Seals • Springs back to almost same size • Aids extraction

  7. AMMUNITION • Shapes • Straight • Bottle neck • Permits more powder • Tapered • Not in use

  8. Ammunition

  9. AMMUNITION • Case Head Designs • Rimmed • Semi-rimmed • Rimless • Rebated • Belted

  10. Rimmed • Rimmed cartridges use the rim to hold the cartridge in the chamber of the firearm, with the rim serving to hold the cartridge at the proper depth in the chamber this function is called “headspacing”

  11. Semi-Rimmed • On a semi-rimmed case the rim projects slightly beyond the base of the case, though not as much as a rimmed cartridge.

  12. Rimless • On a rimless case, the rim is the same diameter as the base of the case • It is known as an extractor groove. Since there is no rim projecting past the edge of the case

  13. Rebated • Rebated rim cartridges have a rim that is significantly smaller in diameter than the base of the case, serving only for extraction. • Functionally the same as a rimless case, the rebated rim provides some additional benefits when considered in conjunction with other cartridges.

  14. Belted • The purpose of the "belt" on belted cases is to provide headspacing. • The extractor groove is cut into the belt just as it is cut into the case head on a rimless case. • The belt as as a rim on what is essentially a rimless case

  15. AMMUNITION • Caliber Nomenclature • Rifled barrels • Lands and grooves • Diameter of bore from land to land • Sometimes groove to groove diameter • Bullet diameter

  16. AMMUNITION • Types of Cartridge • R = Rimmed • SR = Semi-Rimmed • RB = Rebated • B = Belted • No letter for rimless

  17. AMMUNITION • Additional Terms • Magnum = Higher velocity than standard • Wildcat = Nonstandard, produced by small entity

  18. AMMUNITION • Head Stamps (Cont.) • Civilian made with manufacturers symbol • Military made with initials or codes • Year of manufacturing • Match/nm = military match grade ammo • + = NATO • +P or +P+ = High Pressure

  19. AMMUNITION • Caliber Specification • U.S. System not consistent or accurate • .303 Savage = .308 bullet • .303 British = .312 bullet • .30-06 and .308 both fire a .308 bullet • .06 refers to year made

  20. AMMUNITION • U.S. Caliber Designation • Confusing • Not accurate • .38 and .357 • Difference is length of case and grains of powder

  21. AMMUNITION • Black Powder Cartridges • Designated by: • Caliber • Black powder charge • Bullet weight • Examples: • 45-70-405 • Some smokeless powder cartridges used this designation • .30-30

  22. AMMUNITION • Metric Designation • Bullet diameter • Case length • Type of cartridge

  23. AMMUNITION • Head Stamps • All cases have stamps on bases • Imprinted for Identification Purposes • Letters • Numbers • Symbols • Trade names

  24. AMMUNITION • Bullet Powder Weights • Grain = weight not granules • 1 oz. = 437.5 grains • 1 grain = .0648 grams • Bullet and powder weights measured in grains

  25. AMMUNITION • Primer (Cont.) • Non-corrosive/Non-mercuric • Lead Styphnate • Barium Nitrate • Antimony Sulfide • Most U.S. primers contain all three • *Detection of these compounds provides bases for GSR

  26. AMMUNITION • Primers (Cont.) • Rimfire Ammo • No primer assembly • Primer chemical is in rim

  27. AMMUNITION • Propellants • Black Powder • Charcoal • Sulfur • Potassium Nitrate • Charcoal is fuel • Nitrate supplies oxygen • Sulfur creates density

  28. AMMUNITION • Propellants – Black Powder • When powder burns • Gas = 44% • Residue= 56% • Residue appears as dense white smoke

  29. AMMUNITION • Smokeless Powder • 1884 Vieille – French Chemist • Nitrocellulose • Used EtOH/Ether • Rolled into sheets • Cut into flakes • Single base

  30. AMMUNITION • Smokeless Powder (Cont.) • 1887 – Alfred Noble • Nitrocellulose and Nitroglycerine • Rolled and cut into flakes • Double base

  31. AMMUNITION • Ball Powder Winchester • 1933 • Nitrocellulose dissolved • Formed into balls • Different diameters • Appears uniform round, black spheres or ovals • Reflective surface • Flattened round • Irregular • Flattened chips • Wide variation between round and flat

  32. AMMUNITION • Powder Grains • Disk • Flake • Cylinder • Uncoated (Greenish color) • Coated w/Graphite (shiny black)

  33. Ammunition • Powder (continued) • Powders burn at different rates • Gases and unburned grains are discharged upon firing • Grains can be found in clothing and skin

  34. Ammunition Bullet • Originally lead spheres • Musket vs.. Rifle • Minnie ball (Capt.. Minnie, French Army) • Modern bullets • Lead • Metal-jacketed

  35. Ammunition • Bullets • Various shapes • Round • Hollow point • Semi-wadcutter • Wadcutter

  36. Ammo performance-Handguns

  37. Ammo performance-Rifles

  38. Bullet Comparison • Class characteristics • Number of lands and grooves • Diameter of lands and grooves • Width of lands and grooves • Depth of lands and grooves • Direction of rifling twist • Degree of twist

  39. Bullet Comparison • Individual Characteristics • Imperfections on lands/grooves • Score the bullets • Jacketed bullets, more pronounced • Are peculiar to each firearm

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