WHAT DOES FEDERAL 243 AMMO 100 GRAIN MEAN?

Preferred some highly rated ammo for my fresh M&P. Bulk Ammo came out on best with the best costs and quick ,no headache delivery.If All those boys while in the Alamo had ordered their ammo from you men heritage would have turned out differently. I ordered 2,000 rounds on Monday and it absolutely was at my doorway on Wednesday!Federal is my model o