This has been a puzzle to me. But I think that the bullet will go off. My friends say that it wont.

Wrong place. This is the episode discussion. And a bullet is just lead; it will not explode. A cartridge will not either.

The only way a round will go off is if the primer is detonated.. that's what the fireing pin in a gun does..

A hammer simply isn't able to affect the primer, no matter how hard you swing the hammer..

Unless ofcourse you have a spike mounted on the hammerhead, then maybe..

Why should it have to be a spike? The spike would dramatically increase the pressure applied to one spot. But you could also increase the pressure by swinging the hammer harder.

Nooooooooooo, Erik..

Infact, they tested that myth in a previous episode...

"The Build Team first explored the idea of simply shooting the lock to get it open. They set up a locked steel door and a .38 caliber revolver, and were surprised to find that their first shot damaged the lock sufficiently to let them open the door.

Based on the details shown in the episode, they began to test the myth piece by piece: first trying to pull the slugs out of the rounds with their fingers, then trying to set off the case primers by hitting them with the revolver butts.

Both of these proved impossible, so they took apart six .38 rounds, collected a total of 30 grains (1.9 g) of smokeless powder from them, and packed it (wrapped in a piece of cloth) into the keyhole of a second door along with a live primer.

A firing pin was fitted into a gun butt and swung at the primer; after a few adjustments, including the use of black powder instead of smokeless, the Build Team was able to set off the powder in this manner. "

Mythbusters - MacGyvers Magic Bullets