The one I "had been asked about" was a CZ in 500 Jeffery, the owner kept having hangfires with his reloads. the chamber and throat was cast and the throat was long enough that a 600 grain Woodleigh, touching the lands, had a gap of around 1/4" between the base of the bullet and the mouth of the case. the theory was that his loads were not "hot" enough to properly get the bullet going before gas started escaping back around the case, and nor were they warm enough to create a proper seal of the case either.
On asking Winchester (I heard this from the owner, not direct from Winchester) they told him all CZ 500 J's were throated the same. To Winchesters credit, they bought him a box of Norma factory ammo that worked fine. Also, winchester supplied him a load of 130 grains of Win 760 with a 535 Woodleigh, that worked fine as well.
I don't know what the 505's are like at all, other than being expensive.

Regards,
David.