[Quantity of weapon oils at the target as a function of shooting sequence and firing distance].
Five widely used gun oils were tested to see if they could be identified by gas chromatography. All oils in the test produced characteristic gas chromatograms and the test was highly sensitive in tracing the oils. Seven different weapons and various types of ammunition were used to perform firing tests involving an oil sold under the brand name of "Gun pro." The weapons were oiled and wiped dry and subsequently discharged at a cotton cloth target. Series of shots were fired from a maximal distance of 3 m, and the weapon was not cleaned between shots. Grease marks and powder-burn traces were extracted separately and the extracts, after adding an internal standard, were investigated by means of gas chromatography (gas chromatography unit by Perkin and Elmer). The largest quantities of oil were transmitted by indoor ammunition fired from a small-bore rifle. At a firing range of 20 cm, a decrease in the oil quantity could be observed up to the fourth discharge. When the firing range was varied there was a decrease in the oil quantity up to a distance of 80 cm. The first and the second discharge could be distinguished up to a firing range of 60 cm. With increasing force of the projectile and a decrease in the interior length of the gun barrel, the quantity of oil conveyed to the target also decreased. Additionally, the identifiability of the oil was investigated after firing at several layers of cloth and after storage of the samples (no losses occurred after a 1-month storage period).(ABSTRACT TRUNCATED AT 250 WORDS)