Quantity and Composition

Bulk elemental analysis methods have been employed by many workers to do quantitative studies of the amount of residue deposited on the firing hand.

Surveys based on indoor firings of a range of handgun/ammunition combination and sampling of the firing hand using a variety of sampling techniques, followed by analysis using differing sample preparation/analytical methods, gave the following widely varying results for residue collected immediately after firing from one to six shots170:

There is very limited information available concerning the total discharge residue particle population from the firing of ammunition. Available data suggest wide variations in total particle population from repeat tests using the same gun, ammunition from the same batch, the same sampling technique, and sampling promptly.

A series of repeat tests involving the firing of a single round, one handed, with clean hands, and sampling by a standardized procedure gave the following results.170 The mean of six determinations was 5,315 ± 3,622 (68%) for total particles and the mean for the percentage of primer particles was 50.5 ± 14.4

(29%). In another test series the mean of five determinations was 203 ± 81 (40%) for total particles and 65.4 ± 10 (15%) for the percentage of primer particles.

From a single firing of three types of .38" special caliber ammunition the results shown in Table 17.1, for promptly collected residue, were obtained using the particle analysis method.170

The vast majority of the total particle population was due to lead only particles originating from the bullet in the case of the RNL (round nosed lead) ammunition whereas the JHP (jacketed hollow point) ammunition produced a much smaller proportion of lead only particles because the base and side of the bullet are enclosed in the jacket, with the only exposed lead at the nose of the bullet.175 This partly explains the much larger particle population experienced with unjacketed bullets.

Repeated firings with the same gun do not necessarily yield progressively increasing levels of residue nor does the same gun/ammunition combination firing the same number of shots under apparent similar conditions necessarily yield comparable levels of residue.176

It is known that FDR consists of gases and a heterogeneous mixture of particles that contain lead, antimony, and barium either individually or in combination. The size of the particles can vary from <1 to >100 ^m.

To explain anomalies in quantity and composition of FDR deposited under very similar conditions, it has been proposed that most of the mass of the elements detected is contained in a few large particles and that a large variation occurs in the number and composition of these large particles recovered from firing to firing. It has also been suggested that the skin becomes saturated with residue and that the blast from subsequent shots dislodges residue from previous shots.

It is obvious that the discharge process and the subsequent deposition of FDR on the firer are both subject to many factors, the overall result of which is an unpredictable amount of FDR being deposited. What is deposited, if anything, has a varying composition. The overall process is very random.

Was this article helpful?

0 0

Post a comment