I have done this many times- flying after hunting or shooting. Many people do. TSA and other agencies use a device called a itemizer that not only detects explosives, it will tell the operator of the machine exactly what explosives or residue from explosive(s) are present, assuming the device is properly calibrated and the individual operating it is properly trained in its use. Not only is the use of firearms and ammunition (and the proper transport of same) legal in the US, it is fairly common for hunters and target shooters. As an active duty member of the US military, my baggage/contents often came up "hot" for actual "real" explosives due to residue. At airports near military bases, the TSA drones were acustomed to this, especially places like Fayetteville, NC. I just made sure I arrived early enough that they had plenty of time to swab, search, etc. in order to insure my baggage made the trip (hopefully) on the same plane I was on, and I was always prepared to show my military ID, which always seemed to make the Barney Fife types at airports not near a base relax a little bit. I would hope a police ID or presence of hunting/shooting gear would do the same. I would think that non-mil/LE types in an occupation that required using or being near explosives would have some sort of documentation to present to these people. Oddly, the only time I had TSA people acting "antsy" towards me was when I removed my merrell boots and the Xray showed an object inside. I had no idea what it was or how it got in there. In the end, it turned out to be a unit challenge coin I had previously misplaced that had somehow made its way into that boot under the insole. It proved that the insoles worked really good, since it had obviously been in that boot for a long time without me feeling it when wearing the boot. I did clean that coin up before I put it in my pocket.
