Viability of Gun Cleaning Oil Transfer as a Long Distance Gunshot Residue

Typical gunshot residue is composed of inorganic particles partially released from a gun when the gun is fired. Gun cleaning oils are used to clean any remaining particles that build up inside a gun and maintain the gun's functionality. Previous studies show that gun cleaning oil transfers from the barrel to the bullet, then wipes off on the target as the bullet passes through. These organic residues represent a different type of gunshot residue termed organic gunshot residue (OGSR).;This study aimed to validate the data from these previous studies with Hoppes gun cleaning oil, using both a pellet gun and .40 caliber pistol. I performed both visual examinations (iodine fuming) and instrumental analyses (a gas chromatograph-mass spectrometer) to achieve the best results. I also varied the gun cleaning method and target extraction methods to determine the most reliable detection of oil. None of the OGSR results during the firearm trials showed the oleic acid and ethyl oleate peaks that characterize Hoppes gun cleaning oil, but the pellet trials showed a spread of oil exiting the barrel. The oil spread indicates the oil is spraying out the barrel simultaneously with the pellet and likely not adhering to the pellet. Further examinations should be conducted with different firearms and perhaps a colored dye to better reveal any gun cleaning oil transfer.