i have a condor tac vest with a zipper, and i managed to pull a tooth out of the zipper. it has nylon/plastic teeth and one just came out of the fabric it was attached to. i managed to super glue it back in. as much as i like the quickness of putting a zippered vest on, my next one wont have one unless it's a metal one.
mine is like the below ones [random google image search pic]
i don't think a bb would damage it though.. i did get shot hot enough to imbed a bb into the vinyl panel above the molle.. there is a little padding it went into