To add to this, you cannot remove the plastic hand guard at all.

right..

Hello hajo808 and thank you for the report.
This is an issue we are aware of and it has been scheduled for a fix.
Regards,
Geez

This happens to the AK 101 as well, along with the weapons mentioned above.

FWIW, if you swap then relog, you can change handgueard

nop this doesnt work, its not that you could even swap the attachment, you cannot even detatch it: its like a non moveable part, and when you try to drag a new attachment of same class over it the item you are dragging is getting this red - "is not fitting there" background color.

There is a work around for the AK74, paint the handguard and it will pop into your inventory place new handguard on the weapon. HOWEVER, you still can't attach anything to it.

Doubleclicking on the hand guard while having it on your back puts the hand guard on your hands/inventory making it possible to then add a hand guard to the weapon again

Hello hajo808.
The issue has been fixed internally and should be fixed on Steam soon.
Regards,
Geez