How do guns work? Secret stats, I mean.

I see the tranq gun and the upgraded tranq sniper as having a tranq afinity and that's that. Nowhere does it say of any sort of magnitude.

But with the tranq sniper I can sleep sharks, with the pistol, I cannot.

What's that about?

What other secret stats are there? I know that the steel wire trap gun can trap waaaay more stuff than even the large one. Other secret stuff like this?