So for example a federal 210 primer and so on and so on what is the actual meaning behind the 210 Designation I am a press operator at a brass casing manufacturer and I've noticed that we only use 4 different go-no-go snap gauges so are there only different size primers I assume? But there are different types what's going on what system for Designations are used and where do I find the charts or books what am I be looking for I am ignorant and i would like to learn more about my trade.