25mm APDS-T projectiles for 25mm Oerlikon KBB gun.
To quote from the website of the source (suppliers to the cannon-shooting hobby):
High velocity discarding sabot projectiles for the 25mm Oerlikon KBB gun. They are black plastic with a black cap. Upon firing, the sabot breaks off into 3 segments, and the low drag core carries on at high velocity. Core is tungsten carbide, with a zirconium tip. Very impressive pyrotechnic display upon impact! White hot displaced metal arcs out in an umbrella pattern.
In subsequent communications with the source, it appears that there are several variations that are not always easy to tell apart (it'* hard to cut the plastic way to see what'* inside, and of course that ruins the round). The one I got is tungsten metal (not tungsten carbide), and the tip is zinc-carbon alloy, basically a windshield that makes the shape more aerodynamic while permitting the tungsten core to have the optimal penetrating shape. (Analysis by x-ray fluorescence spectroscopy at the Center for Microanalysis of Materials, University of Illinois, partially supported by the U.*. Department of Energy under grant DEFG02-91-ER45439).
Source: River Valley Ordnance
Contributor: Theodore Gray
Acquired: 6 March, 2003