Clamshell (Muzzelverschluss) action rifles are only of German origin, so far as I know. Of course, having said that there will be ten to come forward from other countries to prove me wrong!

The Double Gun Journal article is found in Volume 8, Issue 3 (Autumn 1997).

Here are three views of my clamshell in 9.3x74R. These views will answer Mickey's question about how much the reinforcing web protrudes.

Regards,
Curl