Anyone know if Lee makes a shellholder for the auto prime handheld primer that would work for the 404 Jeffery case?
Or if not, a close second that could work with some dremeling?

I don't have a 404, but about to get started on a 404. I do have a 300 ultra mag, I want to say I had a shell holder to fit, but can't remember. I do remember taking a dremel to the body of the autoprime, If I didnt have a shellholder to fit I took dremel to it. None the less I got the 300 ultra to fit, 404 should also with a little work.

I don't have the Lee Auto Prime, but I do use the Lee case trimmer system and suspect the shell holder info I can provide is probably applicable to the Auto Prime. I use .404 cases for 2 wildcats, hence needed a shell holder for the trimmer. Don't recall how I came onto this, but the .30-40 Krag shell holder fits the .404 case. Incidently, the ultra-mag case has a base (shell holder) the size of a belted mag case, not a .404 case. True, the ultra-mag originates from a .404 case, but it has a turned down, or rebated, rim.