Quote Originally Posted by Richard K View Post
Where I'm stumped is some kind of self sealing face cover so that sand does not drain out after each shot.
3/8" conveyor belt material is self-healing and would work well for your purposes.

A NOTE OF CAUTION:
Don't forget that there are local ordinances that prohibit discharging a firearm within city/county limits. Make sure to check with your local authorities prior to "testing" your new bullet trap.