Spark plug shot out of the head tonight

It's a stupid catchy song that may or may not be my ringtone. MY HORSE IS AMAZING.

ya its a lack of threads in the head, also i have seen some windsor heads with this where it actually had part of the threaded area in the combustion chamber melted away from where the plug had threaded down too far in the combustion chamber and created a hot spot. but its mainly from the lack of threads.