Depends on the bore size you get. The balls can vary from big bore to small, you never know with whitebox. The best barell would probably be a kit; Freak, pipe etc.
Good if you get a decent batch
The effect of getting a bad batch.
Well all in all these paintballs are great for the price. If you get a decent batch they are pretty good for practice. Although one batch I had out of the 3 was full of brittle shelled, dimpled, and thick house paint type fill that wouldn't come off. You might be better off getting some better white box paints, such as Heat or Draxxus rec series. Some times I had bags with all one colored paint but there would be like 2 or 3 odd balls in the bag, like 497 orange balls and 3 green ones. As with all white box paint don't expect much from it, but I'd save the extra 5 bucks and get something a little better, white box is like a box of chocolates, you never know what your gonna get.
Decent for practice, make sure you get a good batch if you are at a feild. If you order them online good luck.