I went and saw the process at Joeken. The actually had to build frames to hold the receivers in place when they heat treated them. And yes there was a certain amount of scaling I saw on the heat treated ones. I'm not sure why the safety is a mismatch on the receiver cover but this would mean that the axis hole is off which would be a big thing. As far as burring, I purchased 10 GT recievers in 5.45X39 and they all came with burrs on the inside of the holes. It only took a minute to clean them up.