Assuming it is the same procedure for the 459 (going on memory here):
CLEAR THE WEAPON. There is no such thing as "gun went off while cleaning." There IS such thing as "gun's owner is an idiot that didn't make sure the gun was clear first."
Hold in your right hand with palm up, muzzle pointing left, thumb on the backstrap and fingers over the top of the slide. Squeeze hard, muscling the slide back until the slide catch pivot pin is lined up with the notch on the slide. You should be able to push out the slide catch with your left hand. You can now remove the slide forward off the frame. Flip the slide over. The recoil spring is held in place on the guide, which is held in a little halfmoon-shaped indentation on the bottom of the barrel. Pull the spring and guide out of the indentation, and it will come off. BE SURE TO CONTROL THE SPRING OR IT WILL FLING ITSELF AND THE GUIDE ACCROSS THE ROOM OR INTO YOUR FACE. The barrel can now be removed out of the bottom of the slide.
When putting the slide back on the frame, you have to push down the three springloaded thingies on top of the frame near the rear.
