Questor, Sounds like your bullets may be to large in diameter or seated to long. The nose may be bottoming out in the die before the crimp can work. I measured my 45's case mouth using jacketed (.451") bullets and get .465". Using lead bullets (.452"), I measured .466". Check your COL, it should be about 1.185". The bullet's shoulder should be flush with the case mouth.
The taper crimp should only be measurable on the first .075" from the case mouth back. It should taper from .466 to the full body dimension of .471~.473" in that short distance.
I use Dillon dies so I have no idea about your Lee TCD.