Preface: I'm using a S&W .45 Colt Mountain Gun
I just got back from the range where I shot 100 rounds of 255 gr, gas-checked, hard cast bullets, pushed by 7 gr. of True Blue powder. No problems whatsoever.
I then shot 30 rounds of Hornady's 255 gr., swaged, "Cowboy" bullets pushed by 6 gr. of True Blue. The forcing cone now looks like mud-daubers set up shop using lead.
Never again Hornady.