One thing to keep in mind is a zipper, regardless of its "waterproofness", is not truly waterproof unless it is one of the super fancy ones and it is installed perfectly. I still shy away from those waterproof duffle bags and waders with zippers. The bag I made is made of silnylon and has a "waterproof" zipper. The problem lies in the fact that there is almost always a little gap in the end of the zipper or if it has two pulls, where the pulls meet. Sure it will shed rain and not absorb water like a regular zipper but the bag itself will most definitely leak when submerged. A dry bag has a rolled top and sealed seams (taped or otherwise) and it is designed to truly be waterproof.
Okay, so do we know if the camp bag is sealed or can it be sealed to provide protection from hiking in the rain or should I be looking into a cover.