The Pedersen device was an experimental weapon attachment for the M1903 Springfield bolt action rifle that allowed it to fire a .30 caliber (7.62 mm) pistol-type cartridge in semi-automatic mode. The attachment was developed to allow an infantryman to convert "their rifle to a form of submachine gun or automatic rifle" in approximately 15 seconds.

The M1903 Springfield, officially the U. S. Rifle, Caliber .30, M1903, is an American five-round magazine-fed, bolt-action service repeating rifle, used primarily during the first half of the 20th century.