There was another thread I read a while back with dramatically accelerated barrel wear shooting PC. The barrel was a drop in conventional rifled in a Glock and the owner was sizing to .356" My suspicion after reading the thread is that the issue was sizing too small and that .357" should have been used.
With lubed boolits, if you size too small you get leading and are encouraged to immediately deal with it. But with PC if you go too small, there is really no symptom. And the same forces that cut the boolit can erode the rifling in the barrel.
The basic concept that is in play is that if the boolit seals the bore, the gasses expand, but do not flow over contact surfaces, thus their ability to transmit heat to the metals involved is quite minimal. Once there is a gap to flow through, gasses can accelerate past at *insane* velocities and impart dramatically more combustion exposure to the materials involved. Lead being weaker than steel of the barrel, lead "gas cuts" and turns into a headache LONG before any barrel damage can occur. But if this problem pops up with a PC boolit, the first symptom you would see is rifling and chamber erosion- and by then it's ugly.
I could be interpreting this whole thing wrong, but if I'm right, the solution is simple, and carries virtually no risk: Make sure not to use a boolit too small.