Are you sure about the caliber? The book by Gander and Chamberlain only mentions a 5 cm mortar (Lance grenades de 50 mm DBT; Granatwerfer 201(b)) but not a 76 mm.
The 50 mm obviously has a m/89 rifle action at the rear of its 200 mm barrel.
Yes, I am. As the 50mm “DBT” uses a propelling cartridge with a special projectile. And the 76mm is the “FRC”.
The rifle cartridge there could be also more of an ignition cartridge rather than a propelling cartridge.
The 76 mm mortar used three different cartridges based on the 7.65 x 54 Mauser case, but none of them was star crimped. One was a very peculiar “percussion cartridge” that projected a bullet a few millimeters from the case and acted as a firing pin. This “bullet” has an enlarged base that was hold at the shoulder after firing (like the piston on a Russian supressed cartridge). It was only used with blank shells.
The 2nd one was a propelling cartridge loaded with a wooden bullet and only used with practice (inert) shells, an the 3rd one was also a propelling cartridge that was only used with explosive shells. It was loaded with a short round nosed, hollow and heeled bullet made of tin.
Alex, as I wrote you before on your question, the ammo in your question to me (the paquet with the given inscription on) was made by AFM, a belgian Laboratorium used from the belgian army (at that time frame working under german occupation)…
As your paquet bears the wording “Ballete etain”, than it contains the 3.variation, from Fedes answer…
It will contain Starter/ or driving cartridges for the 76mm Explosive Shell with the tin-bullet…
Ok, I got further and my suspicions got confirmed.
The 76mm projectiles are slightly simplified German 76mm rounds for the “leichter Minenwerfer” (light mortar) as it was used through WW1.
The Belgian projectiles had no primer in the base and instead just a propelling charge locked in the open base of the projectile (the German types had a base plate with vents and a central percussion priming screw)
I assume the Belgians got inspired by available stocks of German ammo after 1918.