If you look only bullet mass than yes. But you need to remember one thing. 5.45x39 is hollow point round. One hit can make more damage to the body then 2 or 3 5.56x45 hits.
Whole point is that all weapon damage configs, vehicle armor and similar should have been done in MOD itself. I am part of large Arma II PvP tournament Arma Wargames and our dev. team makes our own MOD with all weapon & vehicle configs. This should have been done by DayZ MOD team not BI.