I recall that there were some lots of IVI 5.56mm C-77 (one or more) in the early-mid 90's that did not meet the specs. That was sold off on the US Market, and was quite popular even though it failed to meet specs. (That is the ONLY IVI ammo that I've heard of making it to the Civilian market legally...no 9mm, no tracer, etc....)
That said, in about 2000 or so, there was a lot of ammo used at CFSAC which was....poor. I was scoring for the KF, QM7, and he fired 6 consecutive bull/V-bulls at 300 meters. His 7th shot sailed up into the helmet. We both did a double take on that (it wasn't the first such incident that year) but had to proceed. The next round dropped back into the V-bull ring, along with another 2 bulls after that. I think he only missed the bull on that one shot. There were a number of "fliers" in that lot of ammo, but there seemed to be no external signs of problems with the ammo. *shrug* not much you can do.
Now, WRT the terminal performance of IVI ammo, well, I cannot speak for that as I've not yet been called on to deliver the ammo that way.
The Dominion Arsenals ammo from back in the 60's (65 was a particularly good year if I recall correctly from the old codgers) was abnormally accurate ammunition. I do not recall what the NATO spec is for accuracy requirements of 7.62 NATO ammo, but the DA ammo generally was of such high quality that it far exceeded those requirements. The extra costs associated in producing such high quality ammo were probably part of the reason that DA ended up closing down (just my opinion)
Also....I don't believe that DA ever made any 5.56 ammo in the 60's, though they did make some of the Flechette ammo for the SPIW back then....so it may have happened.
Bear in mind again, that I'm just a shooter, but from my perspective, the issued ammo is accurate enough. I'll let others with more expertise wade in on this now.
NavyShooter