Phil- when they work- they are awesome! And I don't use that word often.
I have four that work very well, though after hours of work by myself and GT!
The reason a million or so were made for WWI was the "artillery" luger and drum for the Stosstruppen. The first time you fire 32 rounds from a correctly functioning snail drum on a stocked L P08, one understands the use and reason for its being.
PS- Gloves are a good idea when messing with the drum, I've rubbed blisters on my hand from loading and unloading.