Talk:Blish lock

Possible Copyright Violation?

The second paragraph of this article appears to have been lifted verbatim from the Web page "Development of the Thompson Submachine gun" at http://www.nfatoys.com/tsmg/web/history.htm --Chuckhoffmann 08:51, 26 November 2005 (UTC)

Does the Blish Principle even exist?

There is some debate whether or not the Blish principle even exists. Some say that in the Thompson SMG the Blish lock functions like a retarded blowback mechanism. I have not been able to find conclusive evidence online (most Web Searches on "Blish Lock" or "Blish Principle" merely link back to this article or any one of its numerous reproductions). Hatcher's Notebook, by J. S. Hatcher, refers to the Blish lock on pp. 44-46, but does not give a conclusion as to whether the Blish principle works as described or not. There's also an article in Small Arms Review, volume 6, issue 3, by Captain Monty Mendenhall that discusses the Blish lock, but I don't have access to this magazine.

Given the controversy, I've re-written the article to be less positive in its assertations of how the Blish lock works until I can find more conclusive evidence. --Chuckhoffmann 23:50, 27 November 2005 (UTC)

The Thompson Autorifle in .30-06 and .276 Pedersen using the Blish principle did function as a delayed blowback but ejection of fired casings was violent. The Blish principle appears to have worked with the Model 1923 Thompson in .45 Remington-Thompson which was reported to have a lower cyclic rate than the Model 1921 in .45ACP (although details on differences between the Model 1923 and 1921 are hard to find other than barrel length and caliber). The Blish principle was not necessary with the .45ACP cartridge, as evidenced by the success of the blowback only M1 and M1A1 Thompsons. A true test whether the Blish principle worked would be to measure the cyclic rate of a 1928 Model Thompson with low pressure, then with high pressure ammunition (if higher pressure caused a hesitation delay the cyclic rate would be lower). I have found no such tests reported. Naaman Brown (talk) 21:12, 19 July 2009 (UTC)

The problem is that whoever wrote that earlier text was misstating the Blish Principle. It's that two dissimilar metals will adhere together better than two identical metals. If I could quote from an article in Popular Mechanics: "He believed that under great pressure, two different metals could adhere together better than two pieces of the same metal. He called it the Blish Principle, around which he designed a breech block which could be used in small arms. He patented his idea in 1915 and Thompson bought the rights to use the idea in his gun. The Thompson used a small bronze H-shaped block which fitted into the gun's steel bolt. According to the Blish Principle, this would slow the bolt's recoil.

There was just one problem: Scientifically, the Blish Principle of metal adhesion does not exist. In reality, the effect Blish was seeing was that his lock merely added mass to the gun's bolt, which, in a blowback gun, simply slows the travel of the bolt. People figured this out during World War II, and British troops using Thompsons frequently removed the Blish lock. Later, when the Thompson was simplified to create the M1, the Blish lock was also abandoned." https://www.popularmechanics.com/military/weapons/a25414/tommy-gun-thompson-submachine/

The Blish principle is junk science. John Simpson54 (talk) 20:44, 22 August 2018 (UTC)