Are you sure the metallics are *rifle* cartridges? My references are packed & I'm not entirely sure this system was used on same, but if so I *am* sure they are mighty scarce. All the metallics I've seen have been handgun rounds and in some calibers these are also relatively scarce.

Could be some Collath shotshells - they have what looks like a wire sticking out the primer hole ( well kinda like that ). Is the case wall of the shotshells very flimsy , and do thay have a raised headstamp that says something like - W. Collath * Frankfurt A.G. and a big number like 5 or 0 at the bottom. The case may have a black wrap around the joint between the metallic base and the paper side wall .

Just a suggestion , dont know a lot about Collath rifle cartridges or if they are constructed the same way ...?