The 3-inch Magnum 20-gauge was a post WW-II item. The first commercial listing for a 3-inch magnum 20-gauge was the Magnum Model 21 in the January 2, 1954 Winchester catalogue. However, there are no 3-inch 20-gauge shells listed in the January 2, 1954 Winchester Ammunition catalogue and price list!?! The Olin brothers and their buddies had been playing around with 3-inch 20-gauge Model 21s for some time before that. In the 1955 Winchester ammunition catalogue the 20-gauge 3-inch Mag. is offered with 1 1/8 ounce of Lubaloy #6 or 1 3/16 ounce of Lubaloy #4. That year the 2 3/4 inch "magnum" shells were introduced with the 1 1/2 ounce in 12-gauge, 1 1/4 ounce in 16-gauge and 1 1/8 ounce in 20-gauge. The 3-inch 20-gauge Mag. offerings remained the same through the 1959 price list. For 1960 the 3-inch 20-gauge magnum with 1 1/4 ounce of chilled shot was added to the offerings, while the Lubaloy loads were still 1 1/8 and 1 3/16. The Winchester/Western offerings in 3-inch 20-gauge shells remained the same thru 1968 where my old catalogues play out.
