I believe you're asking two completely different questions. I would venture a guess that most DR's with iron sights are going to be used at or under 300yards, with the vast majority of shots being taken significantly under that mark. As far as 'effective range', it depends on your meaning. For example, the BPCR crowd are shooting straight walled BP cartridges and sending lead VERY accurately to 1,000 yards and further. I certainly wouldn't stand down range at 1,000 knowing someone was up range sending thumping big pills in my direction! As far as relative 'killing power', for their intended use, certainly less than 1,000. You could probably tie relative velocities at points x through x+n to bullet weight and get your impact energy. As a practical suggestion, I wouldn't shoot my .500 BPE at anything living past about 200. Certainly nothing likely to take umbrage with being shot at and likely to retaliate.