@ H&H
Indeed there are instances where you can radiologically identify certain features of the bullet, depending on the nature of the X-ray view and the condition of the projectile. Here is a basic summary of what you can do with a radiograph if you are familiar with radiological assessment of metallic densities and composite shadows:
If the bullet is intact or only mildly deformed (relative to its condition when it was loaded in the cartridge) then it is impossible to tell whether it is jacketed or all-lead in construction. The only exception to this is if the design of the bullet is such that the jacket does not appose the core intimately all the way around the projectile. The jacket may then be resolved on the radiograph. The same applies to a bullet with an exposed base: it may have a thickened jacketed 'rim' at the base and if the X-ray beam strikes it at the right angle then the jacket will be detected. But in the majority of cases where the typical handgun bullet shape is seen and there does not appear to be any deformity, it is impossible to say whether that bullet is jacketed or not. I will give you an example of the differences in radiological density as evident in different materials and configurations of a sample of projectiles and projectile components. First the photograph:
Note that most of the bullets were fired in a water tank, but the appearances are consistent with my research as regards the density of projectiles that are retained in the human body. The 9mm bullets have very light rifling impressions because they were fired out of a Vektor CP1 which has polygonal rifling.
1 = semi-jacketed flatnose (.357 mag)
2 = FMJ (.25)
3 = LRN (was oversized bullet loaded in a 9mm cartridge case)
4 = Sentry (9mm 60gn)
5 = Winchester Black Talon (9mm)
6 = Speer Gold Dot (9mm. This is the newer version, don't have gn value at hand)
7 = CCI Blazer Aluminium cartridge case (9mm)
Now look at the radiograph:
Bullets 1-3 have the same radiological density on film and there is no way to tell whether they are semi-jacketed, fully jacketed or not at all jacketed because they are not deformed. The overall high density of the lead obscures the density of the jacketing and the jacketing cannot be resolved.
Bullet number 4 is made from solid copper that is nickel-plated. The expanded rim of this projectile is, in effect, a thin piece of copper and it will show as a low density structure on the radiograph. The main core of the bullet is still very dense and cannot be distinguished from a lead core when discussing the density alone. Of course the bullet has a characteristic shape and the size and configuration of the central post makes it highly suggestive that the bullet is a version of the THV, or BAT or Sentry, but being precise about brand is not wise based on X-ray evidence alone in that case.
Bullet number 5 is a Winchester Black Talon and it has the characteristic 6-petal expansion where the petals are of lower density than the core from which they are separated. If a side view of the projectile is X-rayed and the characteristic barbs are seen then I am happy to conclude that the bullet is a Winchester Black Talon (of unknown calibre) based on the x-ray evidence alone. With that view only, the bullet may be mistaken for a Golden Sabre.
Bullet number six is a Gold Dot (a newer version than the one to the right of it). This is a jacketed bullet but even though the bullet has expanded, the jacket cannot be resolved because it is bonded to the core in such a way that apposition is maintained. There is no core-jacket separation. However, the configuration of the expansion and the lack of a resolved jacket makes it quite viable for me to conclude based on X-ray evidence alone (and with no further views necessary) that the bullet is a Gold Dot of unknown calibre.
The cartridge case labelled 7 is interesting because it demonstrates that aluminium is radiolucent (cannot be seen on X-ray). The significance of this is that any bullet with aluminium jacketing will appear as a single density on film even if it is fragmented. The jacket will not be detected and the bullet will appear to be lead only.
As a matter of interest, can you detect (by comparing the photograph and the radiograph) the bullet that has an aluminium jacket?