Don't forget your tricep either. I've got a similar build in my bicep. You can see in my avi. And they do measure to 16" when I'm not lean, and I've measured the left at 15" on competition day around 6% bf. Fantastic peak on the left side, but my arms don't look particularly thick because the muscle is short and my tris are decent but tend to hold water, so again, just looks fat.
Otherwise just keep eating & lifting. I've get decent genetics for biceps so I got good results early on - best results came from 21s. A hitch on doing a lot of focused arm work is increased chance of tendonitis. Be careful and patient. Don't overtrain that area or lose form to push it (easy one is snapping on cable extensions) - too much chance for elbow, forearm, wrist tendonitis as well as sometimes your shoulders. And that shit never goes away.