I would not cull the barrel based on the teslong inspection, I have seen MUCH worse.
I would question the sanity of a Shouldered pre fit as this is a deep discussion unless it is for a Borden, Stolle, Bat, or other top drawer custom action where dimensions are dead nuts same between various actions of the same model.
It sounds like your friend purchased a barrel headspaced for another action, screwed it on his action hoping it would headspace, but it does not.
The longitudinal splits could be from low pressure loads in a chamber with long headspace or work-hardened brass fired in another chamber.
I would question the sanity of a Shouldered pre fit as this is a deep discussion unless it is for a Borden, Stolle, Bat, or other top drawer custom action where dimensions are dead nuts same between various actions of the same model.
It sounds like your friend purchased a barrel headspaced for another action, screwed it on his action hoping it would headspace, but it does not.
The longitudinal splits could be from low pressure loads in a chamber with long headspace or work-hardened brass fired in another chamber.