I learned that carrying bowling balls (mostly because of their density, not their actual weight) is specifically not permitted in general. As is the case for many,many regulations, the actual personnel who check your luggage in, both carryon and check-in, are not aware of every tiny regulation. So, you can sometimes get away with ball(s) as carry-on, but don't count on it. Besides, If something happens to the carry-on overhead bin or its lock or it closes but does not lock, DO YOU WANT TO BE THE ONE SITTING DIRECTLY BELOW YOUR BALL WHEN IT COMES FLYING OUT??
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Just like hand grenades and horse shoes, in bowling you only have to get close ...