[ybrik]

the chief,
use white lithium grease. I see some at cadtire. Brands are lumax, permatex and 3-in-1. These are all lithium greases.
About magazine bb feeding tube not catching-up with the bb feed tube of the metal hop-up.
The hop-up mechanism is not aligned. It could be pushed too much forward by the gearbox when you try to mate your upper to the lower receiver.
In this case, a simple modification is to put a shim between the hop-up mechanism the collar ring (back side)
I had experienced this problem before. It worked though.