The fire bullet

The Tracer round
For the purposes of training a round(Bullet) is filled with some coloured explosive so that the path taken by a bullet can be easily seen with the naked eye especially at night due to the burning explosive behind the bullet as it is fired from the rifle. This helps the firer to adjust his aim accordingly and also to study the ballistics. In simple words it makes the flying bullet visible to the naked eye.
We had one of our instructor from Haryana from the lower ranks who was taking our class on Weapon Training on ballistics. After he finished his class one of us asked,
“Ustaad(Sir), Tracer round kisko kehtein hai?”(What is Tracer round?)
The Ustaad replied,
“Jis round kay shootar(Buttocks) mein aag lagi hoti hai usko tracer round kehtay hain”(The round whose buttocks is on fire is called tracer round)