My First Bottle Bomb Question

I was looking over my brew notes yesterday and realized that I missed a step with my last big porter. I neglected to check the gravity for a couple of days before I bottled to make sure it was good and done. It started at 1.066. It fermented for three weeks at 68F using 16 grams US-05. I measured it at a little over 1.016 at bottling. I primed with about 4oz of corn sugar. What do you figure are the odds of explosive carbonation? It's been a week and a couple of days and I opened one to see what the carbonation was up to. It didn't seem too out of line.