Pete,
Wow, sounds like you were close to being an episode on "1000 Ways to Die".
By the way, for the safety of our reader's, I strongly recommend removing the gunpower from the 50 caiber bullet before soldering it to the chalk holder. Better yet, use something that doesn't explode and blow your body parts off.
Chris:
.50 caliber?!? As in the standard ammo of the military, and the Barrett .50 BMG caliber sniper rifles? That round won't even fit in most people's rear pockets!

From left: .50 BMG, 300 Win Mag, .308 Winchester, 7.62×39mm, 5.56×45mm NATO, .22LR

-Sean