Under the gunslinger's Targeting ability, we find:
Torso: Targeting the torso threatens a critical on a 19–20.
One of my players is a Bolt Ace. Crossbows, of course, already threaten a critical on a 19-20. When using targeting with his light crossbow, does the threat range remain unchanged or double? (And I'm probably right to assume that it wouldn't stack if he gets Improved Critical later.)
there is a large post some-where ( i can look it up if you really want) where a dev explain that classes taht use the same kind of class ability,in the post's case was channel energy, use the same ruling even when the words might seem to defer (it was about having chanel energy "like the cleric ability" yet the class had no cleric levels thous by strict raw shouldn't have any power when chanelling.).
the point the dev made was that abilities from difrent classes that are the same should work the same ,even tho sometime they are worded difrent. and that one shouldn't stick to closly to the exect words.
i think in this case if the only benefit for shooting the torso is getting double threat range(and since gunslinger was out before acebolt was made - didn't take into acount using a weapon with graeter the n20 threat- so it numbered the end threat without saying it's doubled) a bolt ace who uses the same ability should also get his threat range doubled.