Ended up with zeroing the red dot at 50 yards. I was going to move the target back to 100 and see where the POI was, but didn't get around to it. Was having too much fun shooting steel after shooting paper, as well as having other folks shoot it. 
I started with the irons at 50 yards. I took off the red dot so that I had open access to the irons. IIRC, I was about 2" high at 50 yards and pretty much centered on windage, so I was happy. Put on the red dot and proceeded to zero. Should have been pretty quick to zero as I had a rough idea from the irons. Quickly got the windage adjusted, but took a while with the elevation, but that was mostly brain farts on my part where I ended up adjusting the wrong way at first. Thinking back, I probably should have adjusted the elevation on the irons, but wanted to get to the dot.
While zeroing the dot, I had some pretty tight 3 shot groups here and there. Like maybe a 1" lateral spread at 50 yards, so that told me a good amount about accuracy of the gun. When I shot the 5 shot group to confirm zero, I ended up with about a 2" spread. I think I could do better, but the steel was calling. Had a friend be the first to shoot it at the steel, which was a 12" diameter plate at 100 yards. He shot with a front sandbag and could easily get solid hits on the steel. Couple other shooters had the same results and I took a pass at shooting the steel standing and was getting consistent hits. So that told me the zero was good enough for me and I moved onto my AR. I would love to try it out on some steel in the 16" range out to 200-250 yards, but that will have to wait for another day (and a different shooting venue
).
I will eventually shoot the AK at 100 yards and see what the POI is. I also hope to try out some different ammo. I was shooting Wolf Polyformance 123 gr JHP yesterday.
Will also read more about that article posted above. But for now, I'm comfortable that the AK will do fine in getting consistent hits at defensive ranges, or at least what I envision.
i plugged in some data for you into my ballistics app. i used a muzzle velocity of around 2400 fps, for a 123gr Hornady with a G1 ballistic coefficient of 0.266.
i used a iron sight height over bore of 2.0 inches.
environmental factors of 80 deg F weather, 29.5 inHg of pressure, and 78% humidity.
if the AK is zeroed at 50 yards, then:
25 yards, POI will be 0.79 inches below POA
50 yards, POI will be at POA
75 yards, POI will be 0.36 inches
above POA
100 yards, POI will be 0.26 inches
above POA
125 yards, POI will be 0.33 inches below POA
150 yards, POI will be 1.45 inches below POA
175 yards, POI will be 3.13 inches below POA
200 yards, POI will be 5.34 inches below POA