I use CorBon PowRBall ammunition as the first few out of either my G17 or G21. They are very light.... 90 and 165 grain respectively.
I live in light-clothing, warm weather areas (Summer in Ohio and Winter in Florida). I am not concerned about penetrating more than thin cotton, etc. After the PowRBalls, I load the mags with 115 and 185 grain CorBons. If necessary, I have no problems with using 124 grain 9mm or 230 grain hardball. It's all about bullet placement and penetration.