Why are bullet sizes usually in decimal and not just a whole number?

Question

For example, why 5.56mm and not just 6mm? Why 7.62mm instead of just 8?

In: Technology

Answer 1

Bullet design is all about achieving the best results, be it velocity, penetration, stability, wound profile etc.

Designers don’t go ‘lets make a good 8mm bullet’. They start with a design criteria and find the best size for those sets of criteria during development.