I recently purchased an AR-15 SP1 that was manufactured in 1975. I also have two newer versions. I have 2 questions. First I noticed that on my older model when I pull the charging handle back it will click when cocking and if I stop pulling the charging handle all the way back it will rest in a half open position. This doesn't seem to hurt anything but my newer models will not do this. Everything else works great on this gun. It has only less than 1000 rounds thru it and otherwise is in mint condition. Is there something wrong with it? My next question is this. I noticed the quality of the extremities of the gun doesn't seem as good as the newer ones. There are dings and grind marks where the new ones are pristene. These flaws don't appear to have been put on the gun after manufacturing it. The finish is great and all the stamings are very sharp so it has not been re-finished. I'm guessing that there was not as much care taken during the manufacturing process to prevent these issues and I'm also thinking that on the newer ones the dies are changed out more frequently when producing them. Am I correct? I've also seen these flaws on other older models for sale on Gun Brolker. Can anyone answer my questions?