Doable, but it definitely gets harder after 100. At the end of Red Dot Pistol School in AZ, we had everyone hitting man size steel at 100. Some of us were hitting the smaller steel (66% IPSC) at 100. Some of my fellow instructors were hitting the gong at 220. Though the dot makes it easier, its still all about trigger control.
i know i should have taken the 3moa dot instid of the 6moa dot for myself