It is a steel tube with a rim and looks like and looks like a 14 mm (32 gauge) shotshell.
The tube is open on the mouth side.
Rim thickness : 1.95 mm
Rim diameter : 16 mm
head diameter : 14.05
mouth diameter : 13.75
length : 68 mm
The hstp is : 109 44 avu german eagle waA48P 14/4/ dov
Is it a tool for gun smith , a dummy ctge or a part of MG ??