Gunlaker,
We have been making the trip now for six years. In fact we go about three times a year. We have never had anything close to a 'hassle' on the way in to the States. In fact we now know some of them by name and they know the names of our dogs. One of the guys shoots a Shiloh and after we're done the official stuff we talk about loads. Last May, our first trip of the year, the Customs man stepped out, looked at the truck and RV and turned to the others inside and said, "it must be summer." He then asked if we had anything he hadn't seen before and were we over our ammo limit as per the permit. We weren't and we were on our way. I have 700 rounds of 45-70 and 700 rounds of 40-65 plus 200 S&W 40 as well as 200 rounds of .22LR on my Form 6NIA. This year I added 350 rounds of 45-90 and don't expect a problem. I don't always have that much but I have had 1100 rounds with me on the way to Raton and other places one year. Getting out can be more of a hassle but as long as you don't have any purchased firearms, ammo you didn't take with you or components of ammo you purchased you will be alright. Occasionally the Homeland Security people conduct searches of all vehicles leaving and lying to them would be costly. I just filled out and sent my form ATF F 5330-3D the other day. it can be filled out on line, printed and mailed. I have seven rifles and a handgun on mine this year. It'll take two weeks in the mail and three weeks for processing. They prefer a fax number to send it back to. I use a Hunting License ($17) because they do not recognize most of the shoots I attend with the exception of Raton. Give it a try, it's worth it.
Paul