Colic bottles (dr brown/avent)

2 questions..

1. I'm using Dr browns right now but since I'm transitioning to formula I've noticed the milk goes up the straw. And it's not just a little. I've looked it up and it's not because the nipple cap is on too tight, it's not due to heat since I even tried making it cold, and it's also not due to shaking it because I'm not even mixing it in the brp am bottles. So is this normal?

2. I'm wondering how well the avent anti colic bottles are?