Winchester Model 1912 The Winchester Model 1912 ( also commonly known as the Model 12 , or M12 ) is an internal - hammer , pump - action , shotgun with an external tube magazine . Popularly - named the " Perfect Repeater " at its introduction , it largely set the standard for pump action shotguns over its 51 year high - rate production life . From August 1912 until first discontinued by Winchester in May 1964 , nearly two million Model 12 shotguns were produced in various grades and barrel lengths . Initially chambered for 20 gauge only , the 12 and 16 gauge versions came out in 1913 ( first listed in the 1914 catalogs ) , and the 28 gauge version came out in 1934 . A . 410 version was never produced ; instead , a scaled - down version of the Model 12 known as the Model 42 , directly derived from scaled drawings of the Model 12 , was produced for . 410 . Description . The Model 1912 ( shortened to Model 12 in 1919 ) was the next step from the Winchester Model 1897 hammer - fired shotgun , which in turn had evolved from the earlier Winchester Model 1893 shotgun . The Model 12 was designed by Winchester engineer Thomas Crosley Johnson , and was based in part on the M1893 / 97 design by John M . Browning . It was initially available in 20 gauge only ( 12 and 16 gauge guns were not sold until late 1913 ) . The Model 12 was the first truly successful internal hammer pump - action shotgun ever produced . Its tubular magazine was loaded through the bottom of the gun . Empty shotgun shells ejected to the right . Depending on the particular wooden transformer plug installed in the magazine , two , three , or four shells could be stored in the tubular magazine . The magazine holds six 2¾ - inch 12 ga . shells , when no plug is installed , unlike most shotguns of today which hold four or five shells . With forged and machined steel parts , the ultimate reason for discontinuation in 1964 was that it was too expensive to produce at a competitive price . The primary competition at this time came from the much less expensive Remington Model 870 , which had been introduced in 1950 . The majority of " modern " Model 12 shotguns manufactured after 1927 were chambered for 2¾ - inch shotgun shells only , although some specialized models such as the Heavy Duck Gun Model 12 were chambered for 3 " Super Speed and Super X shells ( basically a 3 " magnum ) . The early 20 gauge Model 12 guns had chambers that were 2½ " , and the 16 gauge Model 12 ' s were chambered for a 2 9 / 16 - inch shotgun shell . To add further confusion , some of these early Model 12 ' s have subsequently been modified , with their chambers lengthened to accept 2¾ - inch shotgun shells , while others remain in their factory - stock chamber lengths . Careful inspection by a gunsmith is always recommended to determine whether or not it is safe to fire a modern 2¾ - inch shotgun shell in older Model 12 ' s . Special production examples were produced by Winchester , the U . S . Repeating Arms Company , and Miroku after 1964 through 2006 through specialized gun collector purchase programs , but the Perfect Repeater shotgun was never mass - produced after 1964 . The U . S . Repeating Arms Company ( a subsidiary of F . N . ) announced a complete closing of the New Haven , Conn factory facility in January 2006 , thus ending the Model 12 ' s long and illustrious career at the age of 95 years . Military use . The United States armed forces used various versions of the Model 12 in World War I , World War II , Korea , and in the early part of the Vietnam War , until inventory was exhausted after the Model 12 ' s initial production ceased in 1964 . Versions of the Model 12 were type classified as the Model 12 or M12 for short . Approximately 20 , 000 Model 12 trench guns were purchased by the US Army in World War I , differing from the civilian version by having a shorter barrel , a perforated steel heat shield , and a M1917 bayonet adapter . More than 80 , 000 Model 12 shotguns were purchased during World War II by the United States Marine Corps , Army Air Forces , and Navy , mostly for use in the Pacific theater . Riot gun versions of the Model 12 , lacking the heat shield and bayonet , were purchased by the Army for use in defending bases and in protecting Air Forces aircraft against saboteurs when parked . The Navy similarly purchased and used the riot gun version for protecting Navy ships and personnel while in foreign ports . The Marine Corps used the trench gun version of the Model 12 to great success in taking Japanese - occupied islands in the Pacific . The primary difference in Model 12 shotguns between the World War II trench gun version versus the World War I trench gun version was that the original design , containing six rows of holes in the perforated heat shield , was reduced to only four rows during 1942 . During the Korean War , the Marines used the Model 12 extensively . Likewise , the Marines and Army used the Model 12 during the early part of the Vietnam War , until , due to the Model 12 ' s production ending in 1963 , and the high rate of wartime use , the Model 12 shotguns in inventory were consumed . The Ithaca 37 soon filled the void caused by the end of the Model 12 ' s production , especially among U . S . Navy SEALS . Unlike most modern pump - action shotguns , the Winchester Model 12 had no trigger disconnector . Like the earlier Model 1897 , it too fired each time the action closed with the trigger depressed . That and its 6 - shot capacity made it effective for close - combat . As fast as one could pump the action , another shot would be fired . " See List of individual weapons of the U . S . Armed Forces "