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

>5.56mm and not just 6mm

6mm exists already, in the .243 Winchester and 6mm Remington, as well as many others.

>Why 7.62mm instead of just 8?

Same here. 7.92mm Mauser is frequently called 8mm Mauser, and there are other 8mm cartridges as well, like the Lebel and Remington & Weatherby Magnums.

Very minute differences make pretty big differences when the chamber pressures on modern firearms can exceed 40,000 PSI. Having more granulatity in naming also tends to lead to less instances of someone putting the wrong ammo a gun, usually, although accidents and stupidity happens.