The Canadian Border Patrol has 2 functions:
1. Harass Americans, especially the evil gun owning ones.
2. Ensure returning Canadians have crammed their vehicles with as much crap from Costco as possible.
Both of the above need modification. They harass Canadians too and the Costco check is to make sure the Canadians pay taxes to import the items.
As for the OP, the border guards will ask you whatever questions they feel like. It's best to grin and bear it otherwise they can turn you away. I know it sucks but it's best to smile and get it over as soon as possible.
Long guns can be brought into Canada but handguns can only be brought in if you have a restricted firearms license (Americans can get this license too), have filed the authorization for transport, have the unloaded handgun with a trigger lock in a locked container and the ammunition in a separate locked container.