Some of you guys have talked in the past about arrow shafts cracking to easily by slightly contacting each other during tight groups into target. For those of you who are getting hairline cracks at nock end of shaft, here is a thought to ponder. If you had a bow that preferred level nock travel, but you had the nock point set to high on string. I see that the tail of arrow would be forced down after the shot and the nock on arrow shaft would slam down hard on the launcher arm or arrow rest support. This contact or binding of the nock inside the shaft may be causing the hairline cracks in arrow shafts. Not saying this is fact, it was just a thought that came to me today.