rifleman perk clearly indicates how much armour is penetrated (eg 15% eyc)

but armour piercing mods on weapons just say "increases armour penetration"

any one know how much it does?

*is there a way to change it so for my account or whatever on this forum is in "english english" not "american english"?

All armor piercing receivers ignore 30% of armor.

thank you

so theres no diff between armour piercing receiver and hardened armour piercing receiver other than base damage?

No, there isn't. Of course base damage makes quit a difference.