I run .3 in all my pistols and it makes a huge difference in both range and accuracy. That's particularly true of my KSC G17 for the aforementioned reasons. I've pulled it several times at outdoor games this summer, and I've gotten several 100+ foot kills with it with little issue. As Stalker said, you just aim higher as you would with a real gun.
I also recomend the Firefly bucking for TM pistols. My TM P226 had very poor range with the stock rubber. With a Firefly, I can also easily hit targets 100+ feet away. Before I was lucky to get 75 feet out using .3. But .25s worked great, but I didn't get the kind of range I get out of my KSC with .3 until I switched rubbers.