What am I doing wrong?

[AJC1]

I went through this exact same issue with a Tanfoglio Witness 45ACP. Would chamber factory perfectly fine. I then on suggestion from the CZ forum to try the Lee FCD and that fixed it. Then I started loading with R-P brass and that fixed it w/o the crimp die. From there I started casting my own lead bullets and sized them to .451". I now have zero chambering problems with that pistol.

I find rp pistol brass very thin wall in 38/357, but I haven't measured them across the spectrum. I would not be surprised to find that true in 45acp. Livelife has a chart for 9mm wall thickness that is probably a useful guide for most.
I to believe casting your own is the solution

 

[StrykerByte.45]

You need to seat it deeper.

 

[StrykerByte.45]

The biggest issue you have is too many processes. Size and prime, chamfer the inside only, then charge and seat making sure the bullet stays straight while seating. If it goes sideways you will expand the case. Being careful saves a step. DO NOT CRIMP! At all, whatsoever.