Yeah, I had my steel rod come loose also. To fix it I made a new steel bracket out of 1/4" steel and used a much larger lag screw to hold it to the stock. I also fashioned a spacer to slide in ahead of the steel rod to put it in contact with the bottom of the hole. No problems since then.

The lead plug in mine has not moved.

My .500 is a very early one, SN 500003. I think Merkel beefed up the mounting of the steel bar in later guns.

Curl