DF: I never did do a 404J,but I think it's a good idea.
At the time of this thread, there was a wonderful 404J built on a M70 by Winsron Elrod. I handled the rifle at Cabela's ain Scarborough. Nyrifleman (Doug) on here was looking at it as well.That was why I asked about the cartridge.
I did not buy it,and far as I know neither did Doug....I go back and forth on anything over 375....
Not really something I have any need for; but I do think the 404 is a neat cartridge!