HELP Ignition Key Wont Turn

I have a 1987 635csi. My ignition key wont turn. It moved freely last night and 12 hours later it is frozen. I tried all my keys with no luck. I am about to take a slide hammer to the ignition lock but I dont know if this will even work. Does BMW have an antitheft system for this? I dont know how easy it is to pop a lock but it looks easy on cops. I will be attempting this tomorrow. It is currently 8:00 pm saturday. Any advise would be great
Thank you
Larry