I am having two issues putting an upper together, since this is my first build I'm not sure on a couple of things. The first issue is getting the forward assist to run smoothly. When I have a punch stuck through, it operates properly. As soon as the roll pin is about half in, it seems to bind up. I read a spiral roll pin would solve this. Thoughts? Additionally, I am having issues getting the gas block to slide on. I have read you can freeze the barrel and heat the gas block and it *should* slide in to place. This seems kind of permanent to me. Any ideas?