I bought a mix of 20-round boxes to try out when I first got my Saint (which is my first personal black gun, although I am well versed in black guns from my military service). I'm sorry I can't be too empirical here for those readers wanting suc stats, but here is my anecdotals:
The Saint loves all of it. In fact, one of the reasons I settled on the Saint was its barrel length, twist, lining, and gas system length was the best overall compromise/combination for the entire range of 5.56 (and .223) ammo out there. Having said that, I cannot even remember all the twentys I tried, but I settled on an army can full of Blackhawk, and a lesser but similar quantity of Federal, of both of their green-tips (Both are "XM" type ammo). Only because I 'felt' that my Saint 'liked' eating those, best. Also, because the zeroing distance of my particular municipal range jives with a 250-yd "battlesight zero" for green tips. Don't remember the exact powder and bullet grains size, but it is on the heavier end of the spectrum. I only shoot out to 100/150 yards, and the tightness of the grouping is not limited by the ammunition - it is limited by my eyesight and iron sights. Haven't really put this ammo through optics so cannot say...
I will be switching to a lighter grain when my current stash runs out. But not for Saint reasons. Instead I'll be switching to lighter grains because I read somewhere that the green tips at close range (e.g. home defense) are actually LESS deadly than are the old/M193/lightweight-type bullets. This is because the increased power of the green tip round doesn't allow for proper tumbling up close, and ironically the 'weaker' round is deadlier up close. IDK, just what I read...
