Spitting while bottle feeding?

sam&tm

My 4 week old has started something new. After bottle feeding for a few minutes he starts whining & spitting (literally). Not spitting up, spitting formula all over....mostly in your face. Any idea why he's doing this? We try burping in between & he still takes the bottle do I don't think it's b'c he's full. We are using Born Free bottles w/ level 1 active flow nipples. Could the nipples not be fast enough for him?