Muzzle loader primer shotshells

[Pb4me]

Just waiting for the rain to stop and researching some items. Does anyone remember the brass 12 gauge shotgun shells that's were made with muzzle loader type nipples in place of a primer pocket? They were designed to be primed with regular no. 11 or no. 10 primers as on a regular old time muzzle loader rifle or shotgun. I researched this item and also checked on this forum to no avail. Please excuse if I missed it. Thanks for any responses and for anyone in the storm area, God speed.

[M-Tecs]

The muzzleloader caps don't have an anvil so the nipple would need offset or use a smaller flash hole. Caps don't provide a good seal so you would get blowback into the action.