Have you got a photo of Any peeling ? .They have a very strong solid steel core. A few had the ends peeled back and the core poking through.
Thanks for the heads up Darrol
Ldr, they definitely look like 15mm BESA AP.
Check out this website which has some light documentation on them.
https://sites.google.com/site/britmilammo/15mm-besa/armour-piercing-and-armour-piercing-tracer