Question

I understand that behind the bullet theory as mythbusters have tested with a 45 caliber pistol that dropping a bullet and shooting it at the same time lands at the same time. But i was wondering if this still applies with far greater weapons with more grain behind the bullet. Such as the Barret .50 Rifle. I would like to know if the grain makes a difference and how to prove it doesnt matter the size bullet or rifle/pistol.