Yes - well, maybe.

Abalone armor is pretty tough.¹ While not bulletproof, they're certainly strong, and comparable to some body armor designs currently used by humans (see Lin & Meyers (2005)).

Their shells are made from interlocking tiles of calcium carbonate, reminiscent of certain tiled arrangements for bulletproof vests (the ones made of ceramic). However, the tiles are arranged irregularly, in a way that makes it harder to penetrate them. They're bound together with a coating of protein "glue". Abalone armor could be mimicked to create new types of bulletproof vests, or the creatures could develop a stronger version of it.

So, I think that some sort of bulletproof armor is possible, if it is based on a system like this.

^{1 An abalone is a member of a family of sea snails.}

Yes - well, maybe.

Abalone armor is pretty tough.¹ While not bulletproof, they're certainly strong, and comparable to some body armor designs currently used by humans (see Lin & Meyers (2005)).

Their shells are made from interlocking tiles of calcium carbonate, reminiscent of certain tiled arrangements for bulletproof vests (the ones made of ceramic). However, the tiles are arranged irregularly, in a way that makes it harder to penetrate them. They're bound together with a coating of protein "glue". Abalone armor could be mimicked to create new types of bulletproof vests, or the creatures could develop a stronger version of it.

So, I think that some sort of bulletproof armor is possible, if it is based on a system like this.

I'm aware that there's an ongoing debate in the paleontological community as to whether the armor of ankylosaurs and related dinosaurs was bulletproof. As far as I know, the evidence does not support or destroy the hypothesis that it was.

^{1 An abalone is a member of a family of sea snails.}