The Winchester Model 21 side-by-side shotgun was the last of the American "best guns" to be introduced, and Winchester's timing could not have been worse. It was introduced in 1930, right after the stock market crash of October 1929 which began the Great Depression.
The gun has had a very long run. The last Model 21 from the Winchester Custom Shop was not completed until 1990, and a very few are still being built (as I write this in 2006) under a special arrangement between Winchester and Connecticut Shotgun Mfg. Co.
John Olin became President of Winchester in 1931 and was closely associated with the Model 21 until his death in 1982. He strove to make the new boxlock double superior to the best double guns made anywhere in the world. He wanted it to be compared, not so much to other American doubles, but to the finest British guns (which were the best in the world).
In The Winchester Era by George Madis, Winchesters head gun designer, Mr. T. C. Johnson, is quoted as saying that the gun was " . . . equal in quality to any double model anywhere, and of superior design and craftsmanship. This will be a lifetime gun for the most particular shooter." Mr. Johnson was the director of Winchester's design department during the period of the Model 21's creation, which started in 1924 when the company decided to go ahead with the development of a new double gun. Edwin Pugsley (then Winchester's Factory Manager), and noted gun designers George Lewis, Frank Burton, and Louis Stiennon also had much to do with the development of the Model 21.
The Model 21 represents the pinnacle of American shotgun design, and it is built of the finest steel ever used in a double gun. Unlike other double guns, whose frames were made from case hardened steel, Model 21 frames were machined from a heat-treated cro-moly steel forging. This is why they have a blue finish instead of a color case finish. Model 21 frames are approximately twice as strong as a similar case hardened frame. The frame is also comparatively long, which contributes to the overall strength of the gun by increasing the leverage of the underbolt that holds the barrels to the action.
The Model 21 uses special chopper-lump type barrels made from heat-treated chrome molybdenum alloy steel. These barrels have lumps that are designed to be dovetailed together, then pinned and soldered with soft solder composed of half tin and half lead. This process avoids the high temperature brazing required with normal chopper-lump (or inferior types of) barrel construction. It results in barrels at least twice as strong as normal double gun barrels.
In his Shotgun Book, Jack O'Connor said he had never seen a Model 21 shot loose. He considered the Model 21's dovetailed barrel construction to be superior in strength, and wrote that the Model 21's frame was made of the best material ever put in a shotgun. He wrote, "I believe the Model 21 Winchester double is probably the strongest, most rugged, and most trouble free double ever made."
This opinion was born out by the results of the famous Winchester proof load test. To promote the gun when it was introduced, Winchester went to great lengths to demonstrate the gun's safety, strength and durability.
Winchester purchased a selection of top brand double guns, which included all of the other famous American brands, for a "test to destruction." The technicians at Winchester fired violent proof ("blue pill") loads in all of the guns until they broke or blew up. None of the guns survived more than 305 of these "blue pill" proof loads, except the Model 21. It successfully fired 2,000 of these 150% pressure proof loads without any kind of failure, at which point the test was stopped and the gun torn down. Absolutely no discernible wear or change of dimension had occurred. This gun was featured in Winchester advertisements, photographed with the pile of 2,000 fired proof load hulls behind it.