If you want the very best .28s then go for BB Bastards. Patrol Base stock them and they're the best ammo I've ever used in my WOC. They're pricey, but if you're not shooting more than 800 in a skirmish then it doesn't matter too much.
Also, if it's a feed issue then it could be many things other than the ammo; check that your magazine is seating at the correct height.
My bro just had a bit of a feed issue on a we gbbr turned out to be the little bit off plastic that collects the bb when passing over the mag. Just wanted a small amount of bending down and now is spot on every time.