AS pdogkilr stated, definitely carry copies of the approved forms and not the originals. I have copies in all of my range bags. I've even heard of people who shrunk the copies down to business card size and laminated them, keeping them in their wallets. As long as it's legible, you could shrink them down.
As far as crossing state lines, if you want or need to travel out of state with any NFA item, you have to submit form 5320.20 to the BATF&E and await their approval before traveling. They generally approve these pretty quickly, based on the one time I traveled with two SBRs for training. Interesting point is that if you own a suppressor, you do not have to submit a form 5320.20 when traveling out of state. Not sure the rational behind that.
Last edited by WinterBoarder; March 18, 2012 at 05:40 PM.