Guns are very interesting to me, so I am constantly seeking out information about them. After 20+ years or so, you end up knowing quite a lot. But, as much as I know, it always amazes me how little I know compared to others.
The real experts tend to be expert in one or a few types of guns/shooting. For example, I know almost nothing about long distance benchrest shooting; and a lot of benchrest shooters probably do not know much about cowboy shooting or machineguns. This is obviously an over generalization, but not without some validity.