In The Long Dark the .303 round is the Mark 7 (VII) variant of the round and is deadly if the hunting rifle is at 100% condition. The rounds come in small boxes of ten (more commonly found in game as boxes of 5). The rounds come on metal clips of five which are inserted through the top of the hunting rifle and into the rifle's built-in magazine.
Rifle rounds in The Long Dark are often rare. While a player can easily acquire about 15 - 30 rounds and think they own the world - mistake! Use your ammunition wisely as it can sometimes literally save your life!
Rifle rounds are found either in a small, red and grey coloured cardboard box or alternatively if the player has a keen eye can be spotted singly in fishing huts and other buildings.
Hunting rabbits with the hunting rifle is not very effective, as the rabbits are small and fast, and they can be hunted with stones found on ground instead of ammunition. So you can save your ammunition for more difficult hunts.
Ammunition spawns randomly all over the map, but one potentially guaranteed location would be the derailed carts. Ammo sometimes spawns here, near a corpse.