-edited not an authorized ASC retailer- (in BC, so you get cheap and fast shipping)
Both make premiun BBs that will work great in your gun. I would recommend that you use .25g BBs rather than .20. And if you can afford them, then .28g are even better. The heavier the BB, the more accurate it will travel, and the less it will be affected by wind or obstacles like branches and leaves when used outdoors.