Without precise shot, firing into melee takes a -4 on the attack roll. If that roll is a critical threat, does the -4 make it not so? e.g. a 20 is a 16. Or a nat 20 is an automatic hit and in the case of precise shot the supreme awesomeness blows the fire into melee rule out of the water?
No, a natural 20 is still a hit, regardless of modifiers, and a critical threat. The -4, however, will apply to your confirmation roll, making it less likely that you'll actually get a crit.
I see, thank you!