3 or 5
The Browning Auto-5 is a long-recoil operated semi-automatic shotgun, manufactured in 12, 16, or 20 gauge.
It was designed in 1898 by John Moses Browning, patented in 1900 and manufactured starting in 1902 by Fabrique Nationale of Liege, Belgium. Production continued until 1999, with over 2,750,000 weapons produced. It uses a 3 or 5 round tubular magazine.
The Browning Auto-5 was the first mass-produced semi-automatic shotgun. Its high rear end gave it the name "Humpback". It was used extensively throughout World War I and continued to be used in World War II.