Try getting the bottles with the drop in liners. Less air for them to swollow. Also make sure you are watching what you are eating as well and see if that helps.
Yeah, maybe try a new position for feeding or burping more throughout the feedings, like every half oz at least. I would also bring it up to his dr too and see if there is any issues. My daughter us breastfed but from the breast and she's gotten gas problems sometimes too, and it helped her when I laid her on her back and moved her legs as if she was on a bicycle peddling and that released a lot of gas out of her belly.
I'm not a mommy yet but we touched on some of this in our breast feeding class. Sometimes babies will swallow more air with certain bottles and cause them to be more gassy. Maybe try changing the bottle position or different bottle? I also heard gripe water helps or leaning them foward and massaging their bellies after feedings.