I've actually had this happen.
Not too long ago, I was shooting my mossberg, and had my Ruger security six on my belt. Don't have a real gun belt, so it's not the best setup. So, after a couple slugs, my pants drop to my ankles because of that heavy beast of a Ruger. Fortunately nobody recorded it, but it did get a few laughs. Tightened the old belt up another notch, and my pants stayed put.
This is NOT me in the pic, and he is wearing a belt.