German overlong 10,5cm projectile


Iam just researching german WW. 2 navy projectiles. Now Ive found a 10,5cm projo made for anti sub role. It is very long. The normal 10,5cm projo will be 4,4 calibers long (app. 18") This special Tauchgranate (diving shell) should be about 10 calibers long ( 41"). That is very long.
Anybody here ever has seen or heard about those an overlong shell?
The shell should be fired from normal guns, dive into the water and using a water pressure fuze detonate in an preset depth.

8,8cm - 10,5cm - 12,7cm and 15cm where introduced.

Any idea


If no-one can help here, you might try asking at this forum: It’s a German bilingual site which specialises in German military ammo, including large calibres.