Whenever I've crossed into Canada with firearms, I've printed and filled in the form prior to crossing. It goes a bit quicker if the form is already filled in. You can certainly fill in the form at the border, but again, I do it beforehand.

The link below has the information you're looking for in taking guns into Canada. The form needing filled out is a CAFC 909 form.

The information you're looking for should be found in the link below.

http://www.rcmp-grc.gc.ca/cfp-pcaf/fs-fd/visit-visite-eng.htm

Cameron Hughes