Answer:
6mm AR, a 6 mm wildcat version which shares 6.5 Grendel's casing, but sends a (usually) lighter projectile up to 1,000 yards (900 m). 6.5×42mm, also known as 6.5 MPC (Multi Purpose Cartridge), based on a necked up .223 Remington case.
Step-by-step explanation:
