I called Customs prior to coming back home three years later and was told not only "no handguns" (again), but also my AR and 10-22 (the latter which made the original trip up) would also need to bypass Canada. Further, I was to load all ammunition where it could be readily inspected. Handgun ammunition would not be allowed entry.
The guys at the border were a bit more friendly. Asked me if I had any handguns ("no"), whether I had any ammunition ("yes, here is an inventory list if you'd like to review it first"), and then simply and politely asked me to have a pleasant stay in Canada and I was on my way. Never opened the back of the pickup, but it certainly wasn't worth the risk.
I met my 9mm, .44 Redhawk, AR, and 10-22 a couple weeks later.
Did I just talk to an anti-gun zealot at Customs?