The Glock had quite a thing going with shooting cast bullets and several guns came apart. It seems on the Glock, it can fire without being completely in battery (unlike the 1911 design). Cast bullet residue can (and did) build up in the front of the chamber. When it buildt up enough, it prevented the cartridge from going completely forward and then if the gun was fired, the unsupported, thinner part of the case would blow. Whether the PAT3 will fire without being completely in battery, I don't know. But that may be the reason for the 'no cast bullets' warning. Another possibility is that often cast bullets have a small shoulder where they fit at the case mouth. Standard reloading practice with cast bullets and 1911's is to leave a very small portion of the shoulder sticking out of the case. Possibly if that was done with the rounds in the Kel-tec, they may have indexed on the shoulder, rather than the case mouth resulting in the blown gun that had the starting load of Bullseye. I myself, would not hesitate to use hard cast bullets in reloads, but I would be very careful that the shoulder on the bullet was flush with the case mouth on a .380. 44 Man