I have been reading a book on forensic techniques and have found something that puzzles me.
The book is titled Gunshot wounds: Practical aspects of firearms, ballistics, and forensic techniques, by Vincent J. M. Di Maio, second edition, CRC Press, 1999.
The author says:
On discharge of a weapon, powder grains may be propelled against the base of the bullet with sufficient force to mark the base. Such markings are most evident in bullets with a lead base, that is, lead bullets or full metal-jacketed bullets whose lead core is exposed at the base. The shorter the barrel, the more numerous and the deeper the powder marks. 5 Different forms of powder produce different marks: spherical (true) ball powder produces numerous
deep circular pits; disk powder produces shallow, circular imprints as well as linear markings (powder flakes striking on edge); black powder produces a characteristic peppered appearance (Figure 2.7).
Powder marks are more prominent on the exposed lead base of full metaljacketed bullets than on the base of all lead bullets. Bullets with a jacketed base (partial metal-jacketed bullets) may show very faint powder markings on the base.[/i]
Now here’s figure 2.7:
What puzzles me is that I am sure that base dents like those on (b) are caused by the bullets travelling tip-to-base in the chutes when they are manufactured, and later when they are to be loaded into cartridges. I have seen this to happen only in pointed, jacketed, exposed lead bottom bullets, and I have seen it in unfired bullets.
The author says, as we saw before, “powder marks are more prominent on the exposed lead base of full metaljacketed bullets than on the base of all lead bullets.”
Why this would happen? Why the powder will mark or dent the exposed lead base on jacketed bullets more than the base of an all-lead bullet?
I think this is because only jacketed rifle bullets have a sharp point that can dent the base of the preceding bullet while on the chute.
I am worried to disagree with such an authority as Mr. Di Maio, so I am asking for your opinion. What do you think? Can a cartridge be so packed with propellant as to dent the base of the bullet? Or do flying grains of powder have the force to mark those bases upon firing?