There could have also been issues with how the rear rivets were set or even the rivets themselves. Painting is easy. You can use citrastrip to get all the old paint off, degrease really well and use any variety of high heat engine paints to recoat. There are lots of tutorial forum posts and...
My first thought would be to answer the question of why its over gassed. Is the gas post too big, is the piston set wrong, is there an issue with the recoil spring? There is nothing wrong perse with the receiver. Whomever build it may not have been competent to address the gas issue from the...
From everything I read about them, the TTL prefix on the serial number on the Century Tantals were the ones that had the keyhole issue. The previous owner on mine had tested it and confirmed it had the keyhole issue. I sent it out to a builder for barrel replacement right away. Century was...
Polishing the hammer on an aftermarket FCG can help. Wouldn't worry about the carrier or rails etc. If it runs smoothly, then I would even worry about the hammer. Some of the Tapco and RAK-1 hammers can use a little work is desired, but really not needed.