It looks like you need to replace the charging handle spring and the charging handle arm that taps the cover. Stores like airsoftstore.ca and airsoftparts.ca have these two, as well as the full dytac charging handle kit.
Make sure the screw inside the tube is screwed down. Then you can tighten the ring on the outside. Threadlocker can help stop it from moving around.
You may need to tighten the D-ring at the base. If the barrel still moves around, you can use some barrel shims in between the D-ring and the barrel before screwing it onto the upper receiver.
Apologies for the brief answer. I'm on my mobile
Last edited by -Shade; November 9th, 2014 at 15:54..