John
Looking at importing one from Germany even as we speak!
You are right - in the Fatherland it is known as an 'einstecklauf'. A sub-calibre barrel with an extractor activated by opening the gun. Available in calibres from .22lr right up to some meaty c/f rounds. They feature the ability to be zeroed to the scope and are normally capable of MOA accuracy.
My preference is for a .22lr due to noise considerations - but what a versatile handful it will make!
On cue, I have just had a call from a neighbour with Roe chewing his roses. I fancy tonight will be the ideal evening for a wander!
Now, leather trousers.... check....... Loden Jacket......Huh, where did that get to!!??!!
Rgds Mod