On the flip side, front line folks don't know the manuals inside and out and sometimes make it up as they go along. Having been with another agency that cleared stuff for customs in a previous life, I am somewhat familiar with the process and the levels of discretion involved. There is no reason I know of to refuse entry for bolts; however, it will be an issue if items are under valued or incorrectly identified, rather than vaguely identified. If an inordinate amount of time has passed or there is an indication that the shipment has been catastrophically interupted, a polite e-mail to whichever supervisory level staff you can find in the federal directory will go along way. You do not have to have any reason for doing what you. Destroying lawful items arbitrarily would be a problem.
R