[lurkingknight]

charging handle spring is stretched... you can fix that by cutting a section off and bending a loop out to reattach to the screw... that screw crossthreads easily so be careful, if it does, it'll probably snap in the upper receiver.

Since you're missing the lock on the handle, you will probably need to replace the whole assembly anyways.

The receivers were probably split at some point and the spring was stretched while taking it apart or putting it back together. Depending on the brand of your gun, the charging handle may or may not open the dust cover. Only the ones with the fake bolt lock should pop it open as far as I know, since I've seen them not pop open on g&g combat machines and nylon fiber KA m4s.

Back off the castle nut on the buffer tube, get a long philips screw driver and take the stock off the buffer tube. Tighten the screw inside, then tighten on the castlenut. Don't tighten it too much because it might pull the gearbox out of alignment and you'll lose airseal at the hopup. You can loctite that buffer tube screw into place, you'll need to pull it out and apply some thread locker to it, not too much, you need to pull it off if the gearbox ever needs servicing... just enough to keep the screw from loosening. Don't lose the lock washer between the screw and the plate. If there is no lock washer there, go to the hardware store and get one, it helps the buffer tube not loosen.

You can try tightening the delta ring, but some m4s just have sloppy outer barrels. If you overtighten you can crack the upper receiver and still have the outer barrel loose. You'll need to try tightening it and if it doesn't help, you'll need to shim it, like it was mentioned.

Handguard rails tend to wobble a bit sometimes. Find creative ways to shim it tight once all the fasteners are tightened and properly locked down.