Also, I don't think grenades count because I got 3 hail mary medals earlier and I didn't get the long ranger medal.
Hail mary is calculated different. You can get a hail mary medal from a kill that would NO-WAY have gave you a Long Ranger. Maybe its the distance the grenade travels instead of the distance between you and the target. The grenade flies through the air and falls down. thats usually a lot longer than a bullet that goes straight to the enemy.