I am in same camp as Chuck375 and prefer my classic 505 Gibbs from CZ. I would say 500A2 was relatively popular as these things go prior to CZ introduction of the two big 50 classics.I dont want one myself, but I think the 500A2 is an optimum modern design of a 50 cal DG cartridge. As the above photos show, more/less like a scaled up 458 Lott. Just right size, not rebated like the Jeff or banana cordite size capacity like the Gibbs.

The 500 A square has the same bolt face as the 416 Rigby. A CZ550 or Ruger in 416 Rigby can be barreled for 500A2 with little else done to get a safari grade 50 cal rifle. That about as easy as it gets.

BTW, all cartridge drawing are available on line. I will look for a link and edit this post later. The one I am thinking of is in Spanish. It is free and easy to navigate once you get the hang of it. You dont need to speak Spanish to find the ctg & pics or read the dimensioned drawing.

Home Page:

http://www.municion.org/

Select the Fuego CF tab on left expands the list.
The pick a catagory like : 11.4 -17mm
then pick a ctg like 500Asquare and there you go, A Drawing of 500A2:

Pics from munition.org:
500A2:

500jeff:

505 gibbs: