I was able to take the new to me MK-85 Hunter to the range yesterday. This gun has a bare 209 breech plug and appears unused. After the 1st shot, the spent primer was lying loose in the chamber. With subsequent shots the spent primer remained in the plug and grew tighter, until on #4 when it was not removable with the primer tool. I had to use a vice once home to extract it. Thought I might have to drill it out!
Anyone use a bare 209 conversion with a solution for this? Lube with grease? Enlarge primer chamber?

Pyrodex RS
Winchester 209w