Steve -
IMHO, that will depend completely on the shooter, and the hunting situation. The more power (up to a point) the better if the shooter can "hold it" with the extra magnification and still track and make a good shot. IOW, depends if your shots will be at standing or running deer most of the time (but you need to be euipped to handle both). Easy to track a walking or running deer with lower mag - harder the more mag you have due to a reduced FOV and more critical eye relief). It also will depend on how much time the shooter has put in practicing with the pistol/scope combo at the expected hunting ranges he will encounter, how much in using all the weird positions he'll end up using in the field and how confident he is in his ability with that combo.
I personally probably push it more than the average guy would, but I have been a handgun hunter for a ways over 35 years and have a bunch of field time in almost any situation. On my deer/elk sized Handcannons, I settled on 6X or 7X as the standard, but I also have a couple that wear 3-9X. I can shoot all of these offhand, but always try to use sticks or get a lean or rest on something if I can. My longest range big game pistolas wear 10X, which no way can be shot offhand at game (they are for Pronghorns - so offhand is not an option anyway).
Since I'm diving in with both feet anyway... there are a heck of a lot of better scopes out there than that 4X anyway. Ooops! :eek:
If Javelina chimes in, he'd add a lot more detail, but you get the idea of what my opinions are anyway.
Good shooting pard,
Ladobe :bye: