The Magnum Bullet Dart is a throwing dart which includes a body made from a firearm bullet cartridge of any automatic, semi-automatic, small or large caliber, magnum or regular types. In a first embodiment, a steel point extends from the front of the bullet casing, and a flight shaft of fixed length is attached to the rear of the bullet casing. A user can remove the shaft, and insert or remove weighting material, such as lead shot, into or out of the cartridge through the hole, to adjust the weight of the dart. In a second embodiment, a steel point extends from the front of the bullet casing, and a flight shaft is slidably mounted through a hole in the rear of the casing; the length of the shaft extending rearward of the casing may be adjusted according to the preference of the user. This adjustability does not require the dart owner to purchase different lengths of shafts, thus adding convenience and saving money.