DO NOT DO THIS:
There are threads on this. Use the search.
To sum up the answers:
An FMJ has the jacket applied from the front. An JHP has the jacket applied from the back. If you drill a hole in the front of an FMJ, you've created a copper tube wrapped around a lead core. And probably not bonded all that well. No-one trusts that to hold together on firing. Could even leave part of the bullet in the barrel. However unlikely that is, you don't want to touch off the next round behind it.
Besides, you now have a poorly formed hollowpoint with inconsistent geometry and weight -- having none of the science and manufacturing techniques behind it to make it perform as a hollowpoint should.
Just not worth it.
-Sam
P.S. -- And cutting an "X" in the tip of a bullet does absolutely nothing to its expansion characteristics.