Some of the more modern ones come chambered for high intensity rounds, so you can have a second rifle cartridge of similar intensity in a combination gun, but the caveat is that they should only be used in certain types of action - basically more modern, stronger lock-up ones. The Einstecklaufe I'm interested in, however, are the older type, (though still available new and still popular), that use rounds like 6x70R, 5,6x52, (.22 Savage HP), 5,6x50R and .22 Hornet. These have limited back-pressure and so can be used in more conventional break-open combination guns as a lower intensity second rifle barrel. The .22 Hornet for instance, for use on fox. Or larger ones, (e.g 5,6x50R), can be used for a "Douplette" meaning a quick second shot on a second animal.
Milling out the Drilling extractor slot, to piggyback the Einstecklauf extractor and index the insert is the easy part. But what else needs to be done at the choke end, I wonder, to make a previously fitted one adapt to fit a new gun? Is it as simple as cutting the insert barrel to length and using the muzzle flange adjustments to take up the diameter difference? Or should I send the gun back to Germany for fitting? (the advice I've received). If so many used ones are for sale, they must surely be universal fitting within their gauge. Those on the Forum who know them well will surely have the answer.
