Can you AoO an CMB AoO?

[FanaticRat]

Awhile ago in a game our party was talking with the GM on ways he could make things more challenging for us, and I suggested that, since I'm a gunslinger who is always in melee, the GM should try to exploit my lower CMD when he AoOs my character instead of my higher AC.

Another player countered that, since I had Snap Shot, their attempting to disarm or trip or whatever me on the AoO would in turn provoke an AoO from me, but I can't wrap my head around that. In addition, it seems like doing this would give me more attacks on my turn in addition to my full attack, and the whole thing just seems weird; it seems like leaving myself open suddenly lets me fire off an extra shot if they try to knock my gun out of my hands, but not if they try to whack me on the head.

So, my question is, if someone does an action that provokes an attack of opportunity, and the enemy tries to do a CMB AoO without the proper feat, does the character that originally did the provoking action get to take an attack on opportunity on the opponent? If so, in what order are the AoOs resolved?

[Jiggy]

Yes, it's possible for an AoO to provoke. An AoO always resolves before the thing that triggered it, so it ends up resolving in reverse order.

If you had a pair of duelists with Combat Reflexes trying to disarm each other without Improved Disarm, you'd get a chain of AoOs all triggered within the first duelist's first turn, and resolve them in reverse order until someone's disarm was successful.

[FanaticRat]

Huh. Well ok, I guess. It's just hard to imagine something like a wizard casting a spell, then someone tries to trip him, and the wizard just suddenly stabs the dude in the middle of the casting and goes back to what he was doing, y'know?

I guess he can still AoO me when I reload instead.

[Jiggy]

Well, for that particular case, I think I remember a rule somewhere that you don't threaten while you're casting (and therefore you couldn't take AoOs).