Yeah, i was surprised he used such a weak rifle against the harpies, but it worked so whatever. As far as the big bird goes, he probably thought an eye shot would kill it, its accurate enough at close range. But this is a fantasy setting, maybe an RPG hitting its face would have hurt it but not killed it. But when it opened its mouth the RPG allowed far more damage when swallowed. As far as why he pulled it out now? its because the bullet didnt reach its brain or didnt do enough damage.