Yes, the hammer type matters a little bit. With a standard hammer, there are ways of disabling the gun by throwing the web of your hand in front of the other guy's hammer. This often HURTS, esp. if it's got a hammer mounted firing pin (OW!) but it works...if the guy was stupid enough to cock it.
If he DOESN'T cock it, the way to disable a DA revolver is to grab the cylinder. But the (highly effective) counter to that is a "rollout" - step sideways, drop your elbow and then sharply twist the gun back out of his grip in a "rotary" motion.
The "hand web in behind the hammer" method has a weakness, and it's a big one: the off-hand of the guy trying to grab the gun away MUST come in under the gun and cradle it up into the hand doing the hammer block. In other words, both of the grabber's hands must make a try at the gun at the same time. Which leaves the gunman's hand free to do...whatever. Go for a knife, punch you in the throat, etc.
The "cylinder grab" can be done with one hand, if the goal is to tie up the gun-hand long enough to get a punch or knife thrust or club blow or other nastiness such as the "elbow fold" (described below). Which is why the guy whose gun just got grabbed must sidestep (generally to the outside) while rolling the gun free, to avoid that inevitable incoming "special delivery".
Now, all of this can happen with a slidegun too. The difference is, if you get a shot off while the slide is being grabbed, and the gun isn't pointed at him or doesn't do a disabling shot, the gun is now tied up until cleared. The moment you twist the snubbie away from a grab attempt, it doesn't matter if it fired during the grapple, it'll fire again when the trigger is pulled.
While we're on the subject: one effective way of grabbing a gun is to grab at the guy's gun-hand with one of yours, and with your other hand (or often, your other-arm forearm) fold his ebow up, twisting his whole body around and down by that arm (and breaking it, if possible). By taking his balance away, you prevent any counter attack, be it kicking or punching or knife or whatever.
Done right, it doesn't matter what gun the guy has.
Which is why, the MOMENT you feel your gun get grabbed, you start that sidestepping and dropping and twisting routine. Either the other hand will join that first at the gun, or he'll do the elbow fold and you're really screwed. In all of these cases, you're better off with a snub than anything else BUT that alone ain't a guarantee.
If it's not clear yet: all of this is basic knife technique adapted to the gun in close range messes. At close range, esp. since there's no problem with muzzle contact on firing, your snubby can be "used as a knife".
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