I have shipped many bp related items, mostly via USPS. But never used powder horns. I have some I plan to sell and will, of course, dump the powder in the first. But, I'm wondering if USPS might have mechanical or dog sniffers that could detect the bp residue a ruin the shipping, or worse. Anyone here have some actual, factual knowledge about this. I know I could call the po and ask. But when asking a bureaucrat anything the answer is always 'don't do it'. I was once prohibited from sending a box that once held whiskey bottles. The reason given was that the box might have once held whiskey. The logic to that escapes me.
