I can't tell you about CZ bigbores but can say a little something about reloading them. The 375 and 458 Lott are very easy to reload for. All components are easily available for reasonable prices and are sometimes cheap. When you go to reloading for the 416, the RemMag seems to have cheaper brass prices. As for the Rigby, the cheapest prices have been about $171/100 shipped. The Rem brass is about 1/4 that. 416 bullets are kind of expensive too, there are occasional close-outs on them but not often enough. My solution to shooting my 416 on my Ruger was to shoot cast bullets in order to get the range time to familiarize myself with the 416. I've shot about 250 factory rounds and about 1000 cast loads in my 416.