What is the highest number of rounds you guys might have put through a screw built weapon? Any other problems like screws coming loose after so many rounds or ???

I have only put a couple hundred rds thru each of 2 AMD63 builds to test for function.  Not loctited yet and nothing worked loose.

I put a few hundred rounds thru my AMD63, screws loctited, checked with allen wrench none worked loose.....

I've got over 2000 rounds through my PMKMS without a hitch.  Of course I did silver-solder my screws in, so that's probably not a fair comparison.

Quoted: I've got over 2000 rounds through my PMKMS without a hitch.  Of course I did silver-solder my screws in, so that's probably not a fair comparison.

That's not a bad idea!

Almost done with mine completely, but had a buddy use BLUE loctite not RED and the rifle is 2 years old with about 4000 or so through it and no sign of the screws backing out or waring down.
The blue loctite was just in case he decided to change receivers later. Also always use case hard or stainless screws when on a screw build.
If you use RED loctite be sure headspace is set for the front trunion and all filed adjustments are complete before setting the screws. once they're set, you may need a torch to remove them. While doing this you can ruin the finish or worst yet, damage the receiver while removing the screws.
All and all....I've never seen a screw build go bad if it's done right.