Ammo how is it graded by the makers?

[Joe Silvia]

When you read the specs of most makers match stuff they are all the same. So what is the difference in production between different grades of match grade from a given manufacturer?
Do they set up and run El Supremo then Match, then Practice then Plinker? If so what is the difference between the process?
Or do they run so many lots of the same recipe, Test and assign grade?
Anybody know for sure?
Joe

 

[Jefferson]

test and then assign a grade based on results