So I finally got my franken-gun .308AR build completed a couple months ago. I took it to the range last month to function check and start breaking in the barrel. About halfway through the barrel break-in (about 20-25 rounds or so) I started getting tapped on the nose by the charging handle (ZEV Technologies ambi). I take a closer look at upper receiver where the latch hooks onto and see this:

After posting on another forum and looking into this particular charging handle and trying to find out any other possible reasons the charging handle is moving back during firing, it turns out ZEV's design leaves much to be desired. I dumped the ZEV for a BCM I was able to find (didn't know BCM stopped making .308 AR charging handles) and tried it again. Charging handle still comes back during firing. I can pull on the right side of the BCM (as if shouldering the rifle) and it won't release unless I actually pull the swiveling latch on left side.

This is where I can use some input/advise from any gunsmiths or experienced .308 AR builders:

1. What is causing the charging handles to come back in the first place?

Is it strictly recoil or something else? I didn't see any signs of abnormal or excessive wear when moving the bcg by hand (the two halves separated and holding upper upside down). When firing the rifle I don't feel anything out of the ordinary; no overgassing or whatev, feels like normal .308.

Possible I need a different (heavier?) buffer, buffer spring, or both to prevent over-travel, if that's even the cause?

2. With the charging handle area of upper receiver as worn as it is now, is it still usable if I fix the cause, or it is ruined and the charging handle will move back no matter what now?

If allowed I can attach the link to the discussion I posted on another site so everyone can see the parts used and input already given.