5.56 have around 5 points of damage,6.5 - 10,7.62 - 12.
You really sure that this bullet underpowered?

Yes they are all a bit underpowered actually.
Also I it seems suppressors decrease damage a lot too! This would be completely wrong since we don't have subsonic ammo for the time being.

6.5 damage its not too low, maybe is that the enemy is using a strong vest, because in real life a 5.56 won't kill somebody in 1 hit in the torso

Mass closing ancient tickets with no activity for > 12 months; assume fixed or too trivial.

If this issue is still relevant in current dev build, please re-post.