For a long time it was just too inaccurate (used to have large spread). Now they are very accurate but still have spread (In a good place now).
Only a few days ago did I realize the bullets themselves dont kill enemies in 1 shot as they should. 7.62 is the same as the marksman rifle and it usually kills enemies in one shot to the torso.
To give a good visual demonstration I just recorded myself shooting the guns on the airstrip.
As you can see I placed one-shot range targets beside careless civilians and opened fire. It is obvious how weak these bullets are behaving. I dont think they need their spread change nor explosive rounds (as that is unrealistic). They simply need to kill in one shot, as they should in ARMA.
I have included a youtube video of this.