Homogeneity of Propellants

To investigate the feasibility of conducting chemical comparisons between propellants detected in casework and suspect ammunition, it was decided to determine variations from granule to granule in a single round of ammunition and then to compare burned (discharged) and unburned propellants, to determine what, if any, difference was caused by the discharge process.

Analysis of 20 propellant granules from a single round of ammunition gave the following results. Diphenylamine and three dialkylphthalates were detected in all 20 granules, whereas NG was detected in only 2 of the granules. Peak area ratios of DPA to each phthalate varied widely for each granule. This, and the fact that NG was detected in only 2 out of 20 granules in a single round of this particular ammunition, shows a considerable compositional difference between granules of propellant. It is a possibility that this is a blended propellant. Further work would need to be done in this area to determine granule to granule and batch to batch variations in composition, in order to determine the feasibility of chemical comparisons in each particular instance.

A further test explored compositional differences between fired and unfired propellant granules. Results are given in Table 20.11.

Table 20.10 Firearm surface Coatings

Firearm

Surface Appearance

Major

Minor

Trace

Steyr Grand Rapide .308 Win

Gray, matt

Fe, Mn, P

Ca, S

Si

FAL Rifle 7.62 x 51 mm

Black, gloss

Si, Cl

P, Ca, Si, Ba

S, K, Fe, Ti, Na

Brno Mod 38 x 22 Rimfire

Black, gloss

Fe

Mn, S, Si

Sig Manurhin .243 Win

Gray, matt

Mn, Fe, Ca

K

P, Si, S, Cu

FNC Rifle .223 Rem

Black, matt

Fe

Mn

H&K MP5 SMG 9 mmP

Blue, matt

Si

Mg

Webley Vulcan Air Rifle .22

Black, gloss

Fe

Mn, S

Beretta O/U Shotgun 12 G

Black, gloss

Fe

Mn, Cr, Ca, Si

Beretta 302 S/A Shotgun 12 G

Black, gloss

S

Ni

Fe

Colt AR-15 Rifle .223 Rem

Gray, matt

Fe, Mn, P

Ca, Cl, K, S

Sterling SMG 9 mmP

Black, gloss

Si, Fe

P, S, Mn, Cl

K

MI Garand Rifle .30-06

Gray, matt

Fe

Zn

S, Si

Baikal S/B Shotgun 12 G

Black, gloss

Fe

Cr, K

S, Cl, Si

Aya D/B Shotgun 12 G

Black, gloss

Fe

Mn

K

Gardone O/U Shotgun 12G

Black, gloss

Fe

Mn, Si

S, Cl

Steyr 1904 Rifle 7.9 mm

Black, gloss

Fe, Cl, K

Si

Mn, Cu, S

Walther Pistol .380 ACP

Black, gloss

Fe

Mn, K, S, Si

Ca, Cl

S&W Mod .59 Pistol 9 mmP

Black, gloss

Al

S, Cl, Si

K, Ca, Fe, Ni, Zn

S&W 15-4 Revolver .38 SPL

Black, gloss

Fe

S

Browning Pistol 9 mmP

Black, matt

Fe

K, Cl, Ca

Ruger Speed Six .357 Mag

Black, gloss

Fe

Cr

Ingram SMG 9 mmP

Black, matt

K

Si, S, Cl, Cu

Sussex Armoury Replica

Black, matt

Si, Ba, S

Mg, Al

Fe, Cu

Webley & Scott .38 S&W

Black, matt

Fe

S, K, Cl, Ca

Si, Cu

Colt Pistol .45 ACP

Black, matt

Fe

S, Al

Cr, Mn, Cu, Cl, K

MI Carbine .45 ACP

Black, matt

Si, S, Fe

Ca, Cl, K, Al

Ni, Mn, Cu

Franchi S/A Shotgun 12 G

Black, gloss

Fe

Cl, S

K, Cu, Si

Webley & Scott S/B Shotgun 12 G

Black, gloss

Fe

Si, S, Cl, K, Ca, Cu

Lee Enfield Rifle .303

Black, matt

Fe, Ca

K, S, Cl, Si

Cu, Zn

AR-180 Rifle .233 Rem

Green, matt

P, Mn, Fe

Ca, Cu

Note: See Glossary for firearms/ammunition-related abbreviations.

Note: See Glossary for firearms/ammunition-related abbreviations.

Table 20.11 Comparison of Fired and Unfired Propellants

Phthalates

TrinDPA nDPA butyl-

Sample

NG

EC

DPA

1

2

phos.

P1

P2

P3

P4

A Fired

Minor

Major

ND

ND

ND

ND

Trace

Major

ND

Minor

A Unfired

Major

Major

Trace

ND

ND

ND

Trace

Trace

Minor

Trace

B Fired

Minor

Trace

Major

Trace

Trace

ND

ND

Trace

Trace

Trace

B Unfired

Minor

Trace

Major

Trace

Trace

ND

ND

Major

Trace

Minor

C Fired

Trace

ND

Trace

ND

ND

ND

ND

ND

ND

ND

C Unfired

Minor

Trace

Major

Trace

Trace

ND

ND

Minor

Minor

Minor

D Fired

Minor

Trace

Major

Trace

Trace

ND

ND

Minor

Trace

Trace

D Unfired

Minor

ND

Major

Trace

Trace

ND

ND

Minor

ND

Minor

E Fired

Minor

Major

Minor

ND

ND

ND

ND

Major

ND

Trace

E Unfired

Minor

Major

Minor

ND

ND

ND

ND

Major

ND

Trace

F Fired

Minor

Minor

Major

Trace

Trace

ND

ND

Minor

ND

Trace

F Unfired

Minor

Trace

Major

Trace

Trace

ND

ND

Major

ND

Major

G Fired

Minor

Trace

Major

Trace

Trace

ND

ND

Major

ND

Minor

G Unfired

Minor

Trace

Major

Trace

Trace

ND

ND

Minor

ND

Trace

H Fired

Minor

Minor

Major

Trace

Trace

ND

ND

Major

ND

Trace

H Unfired

Minor

Trace

Major

Trace

Trace

ND

ND

Major

ND

Trace

I Fired

Major

Major

Trace

ND

ND

ND

ND

Major

ND

Trace

I Unfired

Major

Major

Trace

ND

ND

Trace

ND

Major

ND

Trace

J Fired

Minor

Major

ND

ND

ND

Trace

ND

Major

ND

Trace

J Unfired

Minor

Major

ND

ND

ND

ND

ND

Minor

ND

Trace

DPA, diphenylamine; EC, ethylcentralite; ND, none detected; NG, nitroglycerine.

DPA, diphenylamine; EC, ethylcentralite; ND, none detected; NG, nitroglycerine.

Some ingredients such as EC may be present as a surface coating, as opposed to an integral component, and may be blown or burned off during discharge. It is clear from this work that whatever the reasons for compositional differences, whether qualitative or quantitative, any interpretation based on compositional data needs to be approached with caution, particularly when only a small quantity is available for comparison. Any conclusive interpretations would need to be supported by a massive amount of background data.

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