If this problem happens to you, don't drill out the cylinder.
Save yourself a lot of work and mess.
Try the following first:
Put the key into the lock. With the bottom of your fist, hammer the key (as to drive it into the lock cylinder further). If that doesn't work, use the end of a screwdriver or a small hammer. Do it gently if you are using a hammer.
Turn the key. It should turn.
Don't think you can do this forever, but when the problem just starts to happen, this will allow you to turn the cylinder to start the vehicle. At the next opportunity, remove the lock cylinder and get a new one or clean the tumblers to get the crud out.
To take out the cylinder, turn the key to the run position ad push in the little 2mm pin that is facing you on the outer lock housing. It's hard to see, but it's just to the left of the plastic ring that holds the security transponder. Once you push the pin in with a short screw, pull the entire cylinder out with the key still in it.