My experience, either taking 300 chips in my backpack (in their original boxes) or 500 chips in a case, is that they don't know what to make of the X-Ray. They *always* want to know what "it" is and its fun to watch the TSA people try and guess what they are. If I tell them they look at me suspiciously, so I usually don't say anything. So they open my bag, see the chips, smile, show them to a buddy, and let me go.

Never a problem, but always a bag search and sometimes the swab (to check for explosive chemicals).