I have cast a bunch of TLC-356-124-TC bullets. I have loaded a lot of these for my various 9's with good results, beretta, sigs, hk's... I got a strange result when I did a plunk test. I'm using hodgdon data for Titegroup which is 4 gr with a COAL of 1.125. The cartridge sat well above the hood of the barrel dropping in a test cartridge. I then sized case, and it dropped in correctly and sat flush with the hood as expected. I started pushing in the bullet little by little. The bullet finally seated correctly, but I don't think I want to use these bullets even backing down the powder charge to the minimum. I also took loaded a 1.125 cartridge, closed the slide, and then measured. It had pushed the bullet into the case a little ways. I had some 124 gr round nose I had reloaded to the same 1.125 coal, and they dropped in just fine, but the coal was 1.115. I don't like that.
I think I'm going to need to cast some round nose bullets for this pistola. The TC shaped bullets definitely don't seem to fit well.
The Walther PDP is a really nice piece by the way.