I'll admit I'm a shotgun noob for the most part but I saw these mentioned on another forum and was like holy crap I had no idea they made these. Probably nothing new but thought it was interesting.
chaszel.com

30-30 Shotgun Adapters - Shotgun Adapters - https://chaszel.com
30-30 Rifle Shotgun Adapters Allows a 12Ga Shotgun to use 30-30 ammo. For 3″ or 2 3/4″ Chambers Compatible with Break Action Shotguns.
