Unless you're trying to snipe eyes of some enemies with high AC from very far range in the midnight, 150% of Small Guns is pretty much enough for most of combat situations IMO.
Going over 150% can still improve hit percentage under some situations. (long range + high AC enemies + aimed shot + weapons without accuracy bonus + darkness)
I believe the actual chance to hit tops out at 95% in the game engine. Beyond that there are penalties for long range, darkness, and others. Having a high combat skill will help offset these penalties. The game always shows you your chance to hit in combat mode. Observe your chance to hit under difficult conditions. If you want more, keep putting skill points into your combat skills until your chance to hit is where you're happy. You may reach that point before you get to 150%.