Interesting I have never broken a plastic nock during a shot, only when hitting arrows in the target. I use plenty of glue to fill the pocket at the top of the nock taper. I wonder if an air pocket here creates a weak spot?
I have busted plenty of nocks and blew up the shaft a bit more than once, but I have never split one quite like this. This photo is one my dad pulled off. He claims it was at 28 yards and likes to point out it is in the bulls eye.