Forensic Science-Manufacturing, Rifling, and Mechanics of Handguns
Part 1
Handgun manufacturing process
The process of manufacturing a handgun includes initial trueing, deep-hole drilling, rifling, reaming, air-gauging, lapping, straightening, and stress relief. Initial trueing includes cutting the bar into lengths of 30 or 28 inches, then turning on the lathe to position it opposite the ends to ensure that the exterior part is uniformly round. Deep-hole drilling includes drilling the stress-relieved bar using a long, tungsten-carbide bit drill and hollow stem, having one cutting tooth only on one side. Reaming includes bringing the drilled hole to the required diameter and smoothening the interior. Rifling includes putting the rifling grooves inside the bore through the button, broach, or cut rifling. Straightening includes stretching the barrel to ensure that it is straight by using machine processes and a turret press. Air-gauging includes using an accuracy measurement gadget that uses a sensitive snug-fitting analysis to discover exceedingly small discrepancies in bore diameter as it moves through the barrel. Lapping includes pouring a small amount of liquid lead into the bore to build a plug that plugs the bore perfectly. The lapping process eliminates tight spots and takes the inner finish to a polish that looks like a mirror. Lapping is usually done after the last contouring because the diameter of the bore may slightly increase when the metal is detached from the external part of the barrel. Stress relief includes removing internal stresses that may result in drifting impact points and warping as the barrel becomes hot.
Significance and purpose of rifling in the bore of the barrel
The significance of rifling in the bore of the barrel is to exert torque, hence imparting a projectile spring around its longitudinal axis during shooting to stabilize the projectile longitudinally by improving its aerodynamic stability, conservation of angular momentum, and accuracy over smoothbore designs.
Difference between a semiautomatic handgun and a revolver and how to determine the caliber of a handgun.
A revolver is a handgun with a single barrel and a revolving cylinder with multiple firing chambers ranging between 5 and 8 that align with the barrel to fire. The pressure applied to the trigger or the cocking of the hammer makes the cylinder index or rotate, aligning the successive chamber with the barrel and preparing the weapon to fire. On the other hand, a semiautomatic handgun is a handgun that uses the energy from a fired cartridge to eject and extract the used cartridge, put a fresh cartridge into the chamber, and recock the hammer. Semiautomatic handguns have reciprocating slides that a person must retract to compress the recoil spring to cock the striker or hammer. When the recoil spring is fully compressed, it can be expanded by releasing the slide, chambering a round, and driving the slide forward. The two handguns have different calibers. The caliber provides a description of the size of the handgun or rifle bore and the size of cartridges used in different bores. It is measured as the bore’s diameter from one land to the opposite one and is expressed in thousandths and hundredths of millimeters or an inch.
The contrast between a bullet, shell casing, and a projectile.
A bullet is defined as a projectile that comes out of a gun from the front end when the trigger is pulled. A casing is a part that comes out of the side of the gun near the operator. The two parts are known as round, cartridge, or shell. The material of a shell casing may be any type of bullet fired from a pistol, rifle, or shotgun. On the other hand, a projectile is a universal term for a bullet when discussing small firearms. It can also refer to the ball, shot, or shell from artillery or a shotgun slug.
Class and individual characteristics considered when examining a handgun, projectile, or shell casing
The main characteristics considered when examining a shell casing, projectile, or handgun are the dimension and number of the grooved imprints in a gun barrel, the caliber of the barrel and the direction of the rifling grooves’ twist. The overall characteristics can lead detectives to conclude that a bullet or cartridge was fired from a specific category of firearm. Other specific mars can help determine the model and make of the gun used. Individual characteristics include marks produced by unplanned deficiencies during manufacturing or damage, corrosion, or use inconsistencies.
Comparison between a penetrating gunshot wound and a perforating gunshot wound?
A perforating gunshot wound occurs when the bullet completely passes through a person’s body, while a penetrating gunshot wound happens once a bullet enters the body and is trapped inside. Contrastingly, in a perforating wound, a wound is created when where the bullet exits the body (Rubin & Ten Eyck, 2012). After a bullet enters the body, the skin retracts as a result of elasticity caused by the bullet’s pressure. This makes the wound look smaller than the bullet that passed through. The bullet moves in a straight direction, but the direction becomes unpredictable when it comes into contact with the bone. This results in bone-shattering and the bullet may bounce and move to another part of the body.
The characteristics of an entrance wound versus an exit wound.
An exit wound is usually uneven, without an abrasion ring, and with extruding tissue. The wound also bleeds a lot, and the bleeding can, in some cases, be profuse. An entrance wound is encircled by a reddish-brown area of roughened skin (Moore, 2009). This area is referred to as an abrasion ring. The injury does not bleed a lot and is usually small.
Part 2
The characteristics for determining the muzzle-to-target distance
When a bullet comes out of a firearm’s barrel, various compounds, including partially unburnt or burnt propellant particles referred to as gun residue, come out of the muzzle in a cone shape resembling the pellets from a shotgun. The residue may be left on the target’s surface based on the distance between the target and the muzzle. The residue can be examined through various color test methods. The investigator can then use the same bullet or forearm that generated the evidence pattern to create various test patterns to compare the evidence patterns. This helps estimate the distance between the muzzle of a gun and the target based on the agreement of characteristics between the patterns in the evidence and acknowledged test patterns created in the laboratory. Therefore, the proximity of the muzzle to the target when a gun is fired can be determined by determining the size and density of the pattern of residues on the target.
The muzzle-to-target distance in the four ranges
contact to near-contact
In contact range, the muzzle touches the target during the time of discharge, while in near contact range, the muzzle does not touch the target during the time of discharge but is held at a very short distance from the target, usually less than 1 cm (Haag, 2006).
close range
At close range, the muzzle is placed close to the target, usually around 15 to 30 cm during the time of discharge, resulting in gunpowder residue and particles of small metal fragments around the bullet hole (Gitto & Stoppacher, 2021). As the distance between the target and muzzle increases, the pattern of the particles on the target increases in diameter, and the particle dispersion density decreases.
medium range
In the intermediate range, the distance between the muzzle and the target is not too short, nor is it too long during the time of discharge, but is short enough to allow secondary impacts of discharge (Gitto & Stoppacher, 2021). The distance depends on the type of firearm and ranges between 30 cm and 2 feet.
distant range
The distance range is also referred to as long-range and occurs when the muzzle is many feet away from the target during the time of discharge, resulting in no gunshot entrance wound due to the bullet’s mechanical action (Gitto & Stoppacher, 2021).
The characteristics that might exist or not exist in each range
The four ranges create a bullet hole that may cause different types of wounds. Close-range or near-contact wounds have flame burns and hair singeing (Oliveira et al., 2019). Intermediate-range wounds do not have hair singeing or flame burns but show the presence of unburnt particles and some. Distant range wounds are embedded with any accompanying components rather than the lubricant, creating a grease collar (Dodd, 2005). Another distinctive characteristic of distant-range gunshots is that they have a lead shot dispersed over a wider area. Smaller ranges such as intermediate, contact, and near-contact range concentrate lead shot in a smaller area. If the shooter is in close proximity to the target, the bullet follows a straight-line trajectory until the point of impact with the target (Haag, 2006). The other components and gases exiting the barrel will form a cone shape that expands until the point all materials lose forward momentum or strike an obstacle, at which point the path is stopped or altered.
What types of evidence would an investigator document from a handgun at a death scene?
The types of evidence that an investigator would document from a handgun death scene are bullets, gun barrels, and shell casings (Haag, 2006). This evidence is used to determine the type of weapon used, muzzle-target distance, and whether the firearm was functioning correctly.
References
Dodd, M. J. (2005). Terminal ballistics: A text and atlas of gunshot wounds. CRC Press.
Gitto, L., & Stoppacher, R. (2021). Gunshot wounds. Pathology Outlines – PathologyOutlines.com. https://www.pathologyoutlines.com/topic/forensicsgunshotwounds.html
Haag, L. C. (2006). Shooting incident reconstruction. Academic Press.
Moore, S., 2009. Gunshot wounds. Nursing Standard, 24(7), pp.51-51.
Oliveira, J., Ramos, T., Oliveira, E., Lima, D., Ferreira, D., Júnior, C., Neto, N. and Pontes, H., 2019. Gunshot wound at close range: case report. International Journal of Oral and Maxillofacial Surgery, 48, pp.28-29.
Rubin, A., & Ten Eyck, R., 2012. Gunshot Wound Simulation Case. MedEdPORTAL.
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Question 
Approximately 70%–75% of homicides are committed with firearms. Write 4–5 pages that answer the following questions:
Part 1
• Explain how a handgun is manufactured, most specifically the bore of the barrel.
• Why is rifling present in the bore of the barrel? What is the purpose of rifling?
Forensic Science-Manufacturing, Rifling, and Mechanics of Handguns
• Compare and contrast a revolver versus a semiautomatic handgun. How is the caliber of a handgun determined?
• Explain the difference between a bullet, shell casing, and a projectile.
• When examining a handgun, projectile, or shell casing, provide examples of class and individual characteristics.
• What is the difference between a perforating gunshot wound and a penetrating gunshot wound?
• Compare and contrast the characteristics of an entrance wound versus an exit wound.
Part 2
• What characteristics might or might not exist for determining the muzzle-to-target distance?
• There are four ranges. At each range, what is the muzzle-to-target distance?
o contact to near contact
o close range
o medium range
o distant range
• Explain the characteristics that might exist or not exist at each range. For example, a bullet hole will be a characteristic at each range.
• What types of evidence would an investigator document from a handgun at a death scene?
Cite all references using APA citation format.