Cannons were first used at the Battle of Crecy but it wasn't until 1300 that the first basic gun was developed. The first drawing of a gun was found from the year 1326. In 1350, the first "hand cannon" allowed for portability. To increase reliability of lighting gunpowder, flint replaced matches in 1517. Reverend Alexander John Forsyth of Scotland invented the first primer powder in 1805. *You may use Rev. Forsyth for your research paper.
John Hall of the United States created two advances in 1817. The first was the breech-loader. The second was using assembly lines for manufacturing. The biggest benefit with assembly lines was the fact that interchangeable parts were developed, standardizing the industry. Gaspard Kollner of Vienna improved the aim (and created rifles in the process) by adding grooves to the inside of a musket barrel. The next advance was that a cartridge was developed that contained the primer, powder, and ball all in one package. Sam Colt added his touch, and a new gun line, by creating the revolving cylinder or revolver. The first side by side analysis of bullets was done by Philip Gravelle when he created the first comparison microscope. Calvin Goddard used the comparison microscope in 1927 to analyze bullets in a murder case.
Currently, guns have unique identifications based on manufacturer. For instance, Colts produce a left twist groove pattern when all other manufacturers use a right twist groove. Most guns have 4-8 grooves, with 6 being the most common number. Guns can be analyzed in different ways. Most commonly, a suspect is checked for Gun Shot Residue or GSR. This is the residue of unburned particles from the primer and powder combustion. GSR contains antimony, barium and lead in major quantities. Other possible contents are aluminum, sulfur, tin, calcium, potassium, silicon, and chlorine. Cartridge casings are also analyzed. The casings are typically brass, which is 70% copper and 30% zinc. The casing may be nickel coated. Brass is nice because it retains the best latent prints, especially when cleaning solvents or gun oil have been used. Guns are identified by their caliber, which is the diameter of the inside of the barrel (bore) or the diameter of the bullet. European guns are labeled with millimeters. Different types of bullets are used for different purposes. The military uses solid-nosed bullets to cut cleanly through bone and tissue. Hunters use soft-nosed bullets, which open up or blossom when bone is hit. Hunters may also use hollow points, which also balloon out at impact. Weapons and bullets are checked for drug traces, hair, serology (blood), tissue traces, and small fibers. Guns are checked for operability. GSR patterns are interpreted as the residue may for a trail on the route of firing. DRUG-FIRE does all of these comparisons and maintains a national database of information in order to connect cases across state borders.
Remember that guns are emptied, tied up to prevent accidental firing, put in a cardboard box, and personally delivered to the lab. Never stick a pen or pencil down the barrel as it may add scratches that leave marks from the lands. Lands are the ridges and grooves are the valleys inside the bore.