Are they getting cut by something in the mechanism?
Foam splitting is typically caused by high peak pressures in the barrel, but I don't think you would necessarily see that in your setup. Possibly the barrel is too tight?
I cant see anything obvious that would be cutting it, but that doesn't necessarily mean its not there. By high peak pressure, do you mean too much pressure builds up overall, or there is a higher pressure spot in specific? The barrel is fairly tight that may be the issue. However, from the same piece of CPVC, I modded a clearshot with no dart splitting, or at least its rare. However the clearshot does not have a [k25] so its not getting the same power... I am coming to the war this Saturday, would you mind taking a look? Just because you have a lot more experience in this department than i do
Thanks for the ideas.