Yeah, they need crimping alright!
The neck on the .500J is technically too short, given the inertia of the heavy projectile during recoil.
No-one I know, or have ever corresponded with, has been able to get away with not crimping this cartridge.
One 500J-owner, reloading at my bench a few years ago, scolded me for reaching for the deburring tool after case-trimming.
In his opinion the sharp case-mouth helped the crimp to hold!