I maybe wrong, but; I though the 500 AHR was in fact and improved 500 jeffrey. Using 500 jeff brass and start loads.
But, I could be 100% wrong. Or 50% right

I did google up some images to verify the rebated rim.

The 550 CZ is a great rifle. If you tire of the AHR, it could be rechambered for the 500 A Sguare.
I am pretty darn sure on that, but; this is all from memory. There is or was a short version of
the 500 A square thst should also work too. I mean as a backup plan.