I plan to mount one on my cz 858, (kinda like an ak, same caliber), which magnification do you recommend? I was thinking of picking up the 6x42 for the 200 yard cans, and if there is enough room under the scope, using my irons for the closer targets.
On my Saiga 7.62x39 with the 6x42 scope you can use the open sights, but your FOV is quite limited as the scope almost blocks the sights. For my .223 Saiga I went with the 4x24 and using the open sights is not a problem. I didn't double check and wound up buying a scope without the multi-chevron reticle on the 4x24, but the scope is still good and I like the compact nature. My .223 is more of a shot range carbine anyway so it's not an issue. The 7.62x39 is more of a designated marksman setup with the 20" barrel while the .223 has a 16".
If you want a 42mm scope then the 6x would probably be the one to get as it lets you reach out relatively well while still not hampering you too much at close range. My 8x is on my .308 Saiga so that is oriented to longer range shooting.
When you say "200 yard cans" I am assuming you aren't talking pop cans?