Quoted from DaveTheTrain:I've rebuilt and aligned flippers on my other pins but never known one so tight as this.
It's definitely stripped as the keys move a little when inside.
I'll look into vice grips but I really can't see how anything can grip the outside enough to turn it considering the allen keys didn't?
The vice grips will work, you could also Dremel the bolt head sides to make a large flathead screw driver fit with a square shank and put a wrench on the shank for more leverage