When I used to study in tech institute I worked in one laboratory of this institute at the same time. This laboratory reseached different lubes with different additives such as soft metals. One of the best additives for steel-to-steel contact was copper. There is some effect named Selective Transfer. It means copper in lube precipitales on steel surfaces and then copper molecules tranfers from one steel surface to another, but both steel surfaces remain the same and without any wearing. EP number was very high for these kinds of lubes and bearings life lasted several times longer, then bearings with regular lubes.
I guess these kind of lubes would be ideal for gun hinge pins.
You just need to add a bit of this lube on friction surfaces like hinge pin and hook, to make several open-close operations untill friction surfaces become slightly red (copper), then wipe all grease away and go ahead. Just to add some light oil in future and repeat procedure, if all copper comes off from steel.
