Called shots are a darn nice set of rules. Paizo flubbed it a little in my opinion though, since this could have been a good opportunity to differentiate weapons more. Here is a major change I would make:
You may ask why Heavy Bladed weapons do not receive much love in this and I will tell you why. Heavy bladed weapons often have good crit chances, effectively buffing those weapon's power when using called shots, since they can cause the critical effect of a called shot to happen.
Called shots interact differently with different weapon groups now. If a weapon belongs to multiple weapon groups, similar bonuses do not stack.
• Axes: Increase penalties enemies take when inflicted by a called shot by 1. Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase stat damage inflicted by 1.
• Blades, Heavy: No changes.
• Blades, Light: Increase called shot attack rolls by 1. Increase the duration of any penalty inflicted by 1 round.
• Bows: No changes
• Close: Increase called shot attack rolls by 1. When attacking the Head, double this value.
• Crossbows: No changes.
• Double: No changes.
• Firearms: No changes.
• Flails: Increase penalties enemies take when inflicted by a called shot by 1. Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase the duration of any penalty inflicted by 1 round.
• Hammers: Increase penalties enemies take when inflicted by a called shot by 1. Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase the duration of any penalty inflicted by 1 round.
• Monk: No changes.
• Natural: Increase stat damage inflicted by 1.
• Polearm: Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase the duration of any penalty inflicted by 1 round.
• Siege Engines: No changes
• Spears: Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase the duration of any penalty inflicted by 1 round.
• Thrown: No changes.
My group still plays with 1E/2E rules for firing in melee. But we have many house rules and limited feat selection for our style of play.
Called shots is actually a Paizo system from Ultimate Combat mostly for melee weapons allowing a player to target a foe's limbs, inflicting penalties and even stat damage or temporary status effects such as deafened and blind.
Also updates, Axes, Flails, Hammers, and Spears have been buffed greatly. Note that this extra critical range only affects whether or not the called shot is counted as a crit, not whether the weapon itself will deal critical damage. It is only there to let these weapons access called shot critical effects easily. Improved critical does apply to these crit ranges.:
• Axes: Increase penalties enemies take when inflicted by a called shot by 1. Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase stat damage inflicted by 1. Increase duration of any penalty inflicted by 1 round. For the purposes of determining critical called shots, this weapon threatens on a roll of 18-20. This weapon needs to deal 30 damage to qualify for a critical called shot instead of 50.
• Blades, Heavy: No changes.
• Blades, Light: Increase called shot attack rolls by 1. Increase the duration of any penalty inflicted by 1 round.
• Bows: No changes
• Close: Increase called shot attack rolls by 1. When attacking the Head, double this value.
• Crossbows: No changes.
• Double: No changes.
• Firearms: No changes.
• Flails: Increase penalties enemies take when inflicted by a called shot by 1. Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase the duration of any penalty inflicted by 3 rounds. For the purposes of determining critical called shots, this weapon threatens on a roll of 18-20. This weapon needs to deal 30 damage to qualify for a critical called shot instead of 50.
• Hammers: Increase penalties enemies take when inflicted by a called shot by 1. Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase the duration of any penalty inflicted by 3 rounds. For the purposes of determining critical called shots, this weapon threatens on a roll of 18-20. This weapon needs to deal 30 damage to qualify for a critical called shot instead of 50.
• Monk: No changes.
• Natural: Increase stat damage inflicted by 1.
• Polearm: Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase the duration of any penalty inflicted by 1 round.
• Siege Engines: No changes
• Spears: Increase Save DCs associated with called shots by the weapon’s critical multiplier. Increase the duration of any penalty inflicted by 1 round. For the purposes of determining critical called shots, this weapon threatens on a roll of 17-20. This weapon needs to deal 30 damage to qualify for a critical called shot instead of 50.
• Thrown: No changes.
Some categories have no changes - did you feel they were already where you wanted them or ?
In the cases of Blades weapons, those weapons already have great critical ranges, allowing them to easily inflict the critical effects and debilitating blow effects of a called shot. The Debilitating blow requires a threshold of damage instead of a crit, but that threshold of damage normally requires a crit (dealing half a creature's hitpoints in one strike). Therefore, in the case of bladed weapons their advantages are:
-Easier access to debilitating blow
-get to enjoy normal crit benefits and called shot crit benefits often
In the cases of other melee weapons with "no changes" such as the Monk or Double categories, those weapons are not actually unique to those categories, and thus would gain the benefits of another category. For instance Brass Knuckles are a monk weapon and a close weapon.
Also, ranged called shots are quite difficult to pull off due to the additional penalties enforced by the system. Ranged Pathfinder characters also tend to be stronger than melee characters, so this was partially to even those odds.