Airsoft Foil Grenade

I recently saw a tennis ball launcher that used aluminum foil as a one-time valve. They would pressurize the chamber, and when the pressure was high enough, it would break the foil and shoot. I thought that if you pressurized a small chamber with the foil sealing one end of it; then have a nail break that on impact and you have an impact-activated grenade.

So here's what we got:

The orange rectangle is the 1/2" pvc where the bbs go. The diagonal lines at the bottom of that show where the foil seal is. The blue rectangle with the red tip represents a nail, which is attached to the bottom yellow det-plate. The contraption is pressurized through the air valve (purple). At the base there are the two small green things, those will probably be small springs to help prevent accidental detonation. At lastly, there is the big gray rectangle, which is the 3" chamber.

Once I get parts for this I'll build it. My biggest concern is the seal where the nail goes through the pvc... Might glue a O-ring inside of the 3" cap.

For those interested, the parts list goes something like this:

1/2" x ~5" PVC Pipe
1/2" x 3" Bushing Reducer
3" Cap
3" x ~4" PVC Pipe
Air Valve
Springs
Wood
Big Nail (~7" long)

Thanks for reading!

--Ghost