I ran across this reference and thought it might be of some interest.
The source is rusarchives
http://rusarchives.ru/projects/victory65/pages/13_38_1.htm (original page in Russian)
(Google translate page, attempted translation into English)
Google translated text:
"The scheme of aviation gun MS-1 V.L. Sidorenko, L.N. Mikhailov. 1943
Branch RGANTD. F.R.-1. Op.50-5. D.2369. LL.7-9.
The 37.5 mm MS-1 aviation semi-automatic smoothbore gun is designed for installation in the rear fuselage of single-seater aircraft for aimed fire in the rear hemisphere using special sights. Aiming is done by turning the aircraft. "
Below are 2 of the schematics accompanying the text, the first shows some details of the “cartridge” and the second shows the gun with cartridge:
Note the cartridge which appears to be a rocket assist projectile, initially fired from a short cartridge case.
Additions, corrections & discussion are most welcomed.