Eli5: Why are weapons(guns, tanks, some planes) named with numbers and letters?

Question

Eli5: Why are weapons(guns, tanks, some planes) named with numbers and letters?

In: 3

Answer 1

In the design phase the product normally goes through many versions before the production model is approved and sometimes an existing model is improved upon, this makes letter number combination easier than having a whole new name for something that might never be produced.