Tracer .303" MkIIz
The trace compound is in the hollow base of the bullet. It will have a squarer skirt than an ordinary ball (if my mind's eye remembers correctly). The red paint is just a visual indicator for the troops. There is a veritable rainbow of colours - red, white, black, gray, etc
https://en.wikipedia.org/wiki/.303_British#Headstamps_and_colour-coding
Watch your back stop if you are going to shoot it. There was a major fire at a local range when someone decided to get rid of some old tracer.......



























