500Nitro,
In reference to your CZ, I had major feeding issues with my own CZ550 in 404.
The very first top round never got picked up at all!
I read an article from Bob Wolf over in the US & he fixed it with a spacer in the back of the magazine box.
I tried this but with tapered 1/4" block from top to bottom so I didn't lose any magazine capacity with my CZ & yes it works good now.
I am no gunsmith but my thoughts are that CZ have taken too much meat off the feed rails making the front of the cartridge tip up & hence the bolt going over the top of the rear of the cartridge & not picking it up. With the spacer in, it "seems to me" to put more pressure on the rear of the cartridge lifting it up & into correct alignment as the spring is bearing more strongly to the rear towards the unloaded position.
My rifle was a display model that I got for a good price, but it had a faulty trigger & bedding (none at all & a very plain stock rather than a bit more of a "fancy" stock that's supposed to come standard with these rifles) issues as well. All sorted out now!
Tried contacting CZ USA & Winchester Australia - not even a reply, rather piss poor service guys!

After a bit of TLC the action has smoothed out somewhat - still a long way to go yet, but Geez those .404's go in real easy & just fall out even with 2300fps loads!
Guess if we shoot our rigs enough they smooth out hey!!!
Bugger when we don't get to do it enough like me.
That's the "real" issue if you have a tight action......use it more!
Cheers