20 mm brass projectile


strange projectile for ID, brass, hollow. Did anyone meet with a similar one?

thread ~14 mm
d = 19,9
driving band = 20 / 20,55 mm
l = 40,8


12 grooves on driving band.

I can not find a 20 mm weapon that has 12 grooves.

No idea about the number of grooves but with the missing tip / nose cap it’s hard to know what it looked like before it was fired.

I found info from technical conditions about acceptance tests a plugs with a gunpowder from fuzes of tracer 37 and 40 mm ammo Bofors. Technical conditions were in force for the Polish Acceptance Commission in Bofors.
In test a plugs with gunpowder inserts were put in special bullets (~100 g and min. 2,500 atm), which was fired from the rifle 20 mm [???] to special bullet traps. If it is this bullet, it is probably a Swedish construction. I have not found drawings for these technical conditions yet.