In Rust, a hot air balloon has a fixed health pool, and one source says destroying it requires exactly 500 damage. A separate Rust wiki-style source says balloons can be destroyed with bullets or other damage types, but it does not give a bullet count.

Because the exact number of bullets depends on the weapon, ammo type, and whether each shot fully damages the balloon, there is no single universal bullet count from the sources I found. If you want the practical answer for a specific ammo type, I can help estimate it from the damage per shot.