It's an "insert barrel" which will allow me to convert my German Blitz Triggerplate Drilling in 16 x 16 x 8mm Mauser -- into a 16 x 22 Mag x 8mm Mauser.
I bought it from a German gun importer whose mission it is to "Save The Guns" -- as any fine old firearms which are left behind by the deceased "must be destroyed" by the Police if a suitable buyer is not found in a short timeframe. So this U.S. importer works with a gunsmith over in Germany to claim and literally "salvage" some fine old Germanic or Austrian guns when local buyers are not readily found in Germany. They ship them over here to -- "Save The Guns". (A noble cause I'd say.)
Here's what the highly engineered device looks like... (less than 8" long)
Following some ideas on threads from the DoubleGun forum, I was able to fit the extractor (painstakingly hand filed) to my Drilling's extractor, set the headspace and then slightly file on the 3 adjustable bearing pads to allow it to chamber correctly. The headspace is all set and an unfired 22 Mag chambers easily, and extracts well, and the action closes just fine with no binding evident.
I'm not sure how it will shoot yet, but I have read that bore-sighting is the preferred way to "get it close". Right now, it isn't hitting the shotgun barrel -- which is great -- but I think it is aimed a little too low. Lacking any installation instructions at all, I am taxing my gunsmithing, logic and observational powers to do what I think needs to be done. I believe I will have to adjust ("file" some more) the two upper adjusting pads as they are both bottomed out and I cannot adjust one side to correct for windage. For one to move more left, the other one has to move right by that same amount. I also think the elevation adjustment, via the larger bottom adjusting/locking pad, will need some more work too; but in order for that to lift the front of the barrel, the top pads will have to give some. But as noted, they're a snug fit for now. I'm guessing this is probably pretty common when fitting a new Einstecklauf, where it was never fit to another barrel before. I'll test fire it to make sure it works, but will hold off on any future filing or fitting until I get some feedback from members of the German Gun Collectors Association which I'd joined months ago.
Well, here it is. All installed, locked in, and with the 3 chambers "loaded for bear" -- or should I say for "Fox, pheasant and red stag".
With this Drilling, I'll be all set for squirrels, rabbits, fox, partridge, pheasant, coyotes or even deer with just 1 gun.
Old No7
and another thing, I may be a Limey but I don't like warm beer 
