WHAT DOES 17 HORNET BRASS MEAN?

I've a Savage 17 Hornet. It is an extremely successful minimal cartridge. I like it but for me a 20 Sensible in an AR has all but replaced it.All have a comparatively minimal sectional density and ballistic coefficient, the equal of the .308 bullet that weighs ninety five grains, which implies they decelerate real fast more than the very long haul.