These special cartridges were recently made for the Martin-Baker MK-J5D ejection seat system used by the Grumann OV-1D Mohawk aircraft, of which the Argentine Army bought 25 units in the early 1990’s. Above is the 7536-1 for the drogue gun (a modified version of NAVAIR dwg. 2520002) and below is the 16650-1 for the guillotine (a modified “Cartridge, Impulse, Mark 66 Mod. 0”). The head of this one is rimless-grooveless and the rim is actually the case mouth.
I think I may have told this story before, but back in the late 1990s, I was at Naval Ordnance Station - Indian Head (MD) (I think it is now called NSWC-Indian Head), which is south of Washington DC. I went through their seat ejection cartridge manufacturing operation, as they loaded their own. They used .38 Special commercial cases (Remington, as I remember), but actually made their own primers, which they QA tested extensively before loading. They felt the quality level of commercial primers was not high enough to meet their reliability standard. As I remember there were 5 or 6 people working there.
Not directly related to this thread, but connected…
Just after WW2 when M-B were developing their first ejector seats for jet fighters they could not get enough black powder for the propellant cartridges, so they asked Woolwich who turned out all the old magazines and broke down all the old British blackpowder cartridges they had. Martini, Gatling, Gardner, all sorts were broken up for the powder to be reused in early ejector seat development.
Why did they use black powder and not smokeless? Did they want less of a shock for the seat itself? I know close to nothing about ejection seats.