I have talk with Dr. Mank, the owner of Brennecke once about using Brennecke slugs in pinfire shotguns. Mister Mank tells me that the brennecke slug was designed to be safe in any shotgun barrel, safe to shot with shotgun cartridges.
You may imagine that no shotgun, capegun , drilling was build in germany and austria where the gunmake dont think about the use of slugs in it.