I picked up a set of the new Bulgarian plum furniture that's being sold in the EE. The lower HG is moulded over a piece of tin that sticks out in the front. It matches up fine to my hand guard plate that slides over the barrel

and over the edge of that tin lip but it does not push it up tight. The lower guard can be pushed up towards the barrel.

I know a pic is worth a 1,000 words but I can't get one at this time. I'm hoping someone will know what I'm talking about. Normally that plate pushes on the face of the guard and would keep it from moving.

The gun is a WSAR and the HG is Bulgarian.

Look at the "tin" heat shield. It should have a raised "hump" in the middle of the end. This works to put tension on the barrel and keeps it from moving up and down. On mine I had to bend it up more for a tight fit.