Re: Noveske upper to lower fit
If you replace the front pivot pin with a shoulder bolt that you can tighten up, you can eliminate all that play. Most hardware stores sell a quarter inch shoulder bolt that will fit perfectly for about $2.00.
For those that don't know, the shoulder bolt looks sort of like the push pin, but has a precision ground smooth surface to go through where your pivot pin goes. There is about a quarter inch of threads on the side of the receiver where you put a washer and an acorn nut. When you tighten this acorn nut up, movement between upper and lower receivers disappear.
You don't have to tighten it up much, and you won't wreck anything by doing this. I have used them for over a decade, and any of my friends who whom I have shown this to have also had great success with it. However, it is a nuisance to have to take the bolt out to separate the two receivers for cleaning.
You just have to decide if it is more important to eliminate the play between receivers, or to have a rifle that is quick and easy to disassemble and clean.