This article was originally posted on Thefirearmblog.com
In this article, we’ll take a look at an experimental Soviet cartridge (5.6x60mm) and an interesting technological failure of the manufacturing process. This article is based on one written by Nikolay Dvoryaninov, a renown Russian ammunition and firearms expert. Dvoryaninov’s article was published in Kalashnikov Gun Magazine.
The 5.6x60mm cartridge was a mystery even for the owner of the case and author of the mentioned article – Nikolay Dvoryaninov. He found it in the collection of his father (Vladislav Dvoryaninov) who is an iconic Russian ammunition designer and for many years was the head of the ammunition department of TsNii TochMash. Vladislav Dvoryaninov is responsible for the development of many Soviet/Russian small arms cartridges and experiments in the field of small arms ammunition.
Nikolay’s research showed that this is most likely the only surviving case of an experimental cartridge made in 1941. Back then, the Soviet engineers were experimenting with a semi-auto rifle chambered in the 5.6mm caliber. One of the Soviet prooving ground reports mentions about this cartridge and says that it is too powerful and resulted in a bent receiver of the firearm (most likely a rechamberedSVT rifle). The report states that the advantages of the new cartridge over the standard one (7.62x54R) may only be significant in close ranges which makes the further development of the cartridge unreasonable.
Further examination of the case shows that it is not a necked down 7.62x54mmR. This case has thicker walls, smaller primer pocket and no markings on the case head. The case length of 60mm is probably chosen to use scaled down to 5.6mm and similarly shaped bullets as those used in 7.62x54mmR cartridges. With that kind of 5.6mm bullet shape, the 60mm case would allow having an overall cartridge length identical to the 7.62x54mmR which would allow to easily rechamber the existing semi-auto rifles and use the same actions.
That’s pretty much all we know about this cartridge. However, there is another interesting thing about this cartridge. Note that the neck has an unusual crown shape. The reason it looks so is that when making the cartridge, they failed to properly anneal it after necking it down. As a result, the residual stresses made the neck to crack over the time. According to Nikolay Dvoryaninov, this was a common problem with the experimental small caliber cartridges back in the day. Eventually, they figured out how to anneal these cases properly and this surviving sample is a rather curious example of the ammunition manufacturing technologies history.
Dvoryaninov N. (2018, February 20). “Таинственная незнакомка”. Kalashnikov Gun Magazine. Retrieved from: https://www.kalashnikov.ru/tainstvennaya-neznakomka/
Images from www.kalashnikov.ru