Anybody know what these cases are for?

[Typecaster]

I found these in with a large batch of .223 milsurp brass. At first I thought they were for a Berdan, but then I realized the bevel is on the wrong side of the rim. They are Berdan-primed, though (3 holes).

I.D. of mouth—.288
OAL—1.586
O.D. of rim—.510
Rim thickness—.125
Headstamp reads: MK2A4 6-70 RVA17-46

[MakeMineA10mm]

Just a guess, but I'm betting some sort of priming cartridge for an artillery piece. I know that some of the saluting-type (non-)guns that fire blanks (like during ex-president's funerals) still use a percussion system that takes a priming cartridge.

[only1asterisk]

Just a guess, but I'm betting some sort of priming cartridge for an artillery piece.

That's exactly what it is. The case holds 19 grains of blackpowder.

Search for MK2A4 on google and learn all you ever wanted to know.

David

[schutzen]

These are Mark 2 A4 Priming cartridge for artillery shells. It contained 19 grains of black powder to ignite the powder charge of 105MM and 155MM arty shells.

Check the US Army Artillery School Ft. Sill, OK.