This is the first time I've looked at it, and I already don't like the existing "Disarm" rules, assuming we're talking about the maneuver in Arsenal, pg. 159.
You can't actually disarm someone unless you first defend using Full Parry at a -4 DP modifier, and successfully parry the attack. At that point, their weapon is on the ground.
Since you need to stop the attack with parry, and parry is against melee attacks only, unless they're pistol-whipping you, doesn't look like you can use that to grab their gun.
This is why, instead of coming up with maneuvers, they ought to have done a better job pointing people to the following:
When a shot is called, and pending the gamemaster's agreement, the player character has the choice to:
* Target an area not protected by armor. ...
* Target a vital area in order to increase damage. ...
* Knock something out of the target's grasp. The attacking character receives a -4 dice pool modifier on the attack. If the modified Damage Value of the attack exceeds the target's Strength, the target loses his grip on the object. The gamemaster determines whether or not the object is damaged and how far away it is knocked.
* The gamemaster may also allow other specific effects for called shots if he chooses. ...
Emphasis mine.
Using called shot, you don't wait for them, you don't worry about parrying, you can use a weapon (or not), you can perform it at range or not, and you don't care WHAT he's wielding. For that matter, under that last heading, for a -5 or -6, when unarmed, I might very well say "sure, you can grab his gun instead of knocking it away from him".
