First couple pics are of the loading gate from a Winchester 94. The shiny part was polished to deburr and slick up the surface. That surface rides against the rim of the shell thats was either just loaded or next to feed. The angled surface cams the shell forward slightly to load another round. The rib along the back edge can also stand a little cleaning up on many of them. It doesnt take much, just remove most of the tool marks from the first part indicated (circled), and mainly deburr the rib father back (from the arrow back). Pre-war 94's load slick as can be. The finish on that part is all I can really tell is different as far as loading the magazine.
The toughest part of removing and replacing the loading gate is getting the screw back in square. The gate is bent for spring tension, and getting the screw started straight is the most important thing. I sometimes let the front of the gate get slightly out of its hole until I get the screw started a couple threads, then push it into place and finish torquing the screw carefully. They are small fine threads, dont get carried way torquing. I've been able to get the gate out and back in without taking the action aprt. if youre going to slick up the lever, then do the gate when its apart. Its easier to get the rear part of the gate in place for the screw to start straight. 94's arent hard to take apart once you know the basic procedure. I had my first one at about 13 or 14 and figured it out pretty quickly in the pre-youtube days of the '70's.
To help them close easier on an empty chamber, polishing the front edge of the lever, and the little bump at the front forward edge help.