they stopped me for c4 residue once on a carry-on bag. So the bomb scanner thing works IMO. I would have been fucked without travel orders (it was a range bag)
I also got stopped flying in full class A's for the dammits in the back of all my pins. I refused to remove them and made a huge scene. One of the air crew offered to hang it in the crew locker for the flight, and I agreed.