Zero leveled is where the crosshairs are matched to the bore at 0-0 on your scope. This will keep you from having to make major adjustments when your shooting. Granted range and drift will always be issue's, but for the battle sight zero movements should be minimal.
I still don't know if it got zero'd, he told me he had to shimm it, and he showed me the boresight when I got there. I will tell you when I get to shoot it.
I built one of these on a retired sniper several years ago. It was a tack driver--killed on the front end, and wounded on the back end. Shot dead on at 200 yards, and routinely rolled coyotes at that range. PITA to carry and handle in the field, and the safety is nearly impossible to use.
Got to reading about Stalingrad, and had to have it. Traded it for a nice Springfield 03-A3. CB