Also Application for Temporary Importation of Firearms and Ammunition ATF F 6NIA (5330.3D)is no longer printable via computer. The form must be downloaded, printed out and information printed or typed using a printer.
Feel free to contact the Firearms and Explosives Imports Branch and ask why:
Phone: (304) 616-4550
Office hours: 8 a.m. to 5 p.m. EST
Monday through Friday (except federal holidays)
If you have questions on the process for bringing a firearm into the U.S. as a visitor, feel free to visit the page I have posted. It answers most questions.
ATF Form 6NIA Guidance