Black is not going to ruin the cases..I have some 45-70 brass that is 5 to 6 years old..You have to wash out your cases and dry them as well..Some of my 45-70's have been loaded 30 times or more..I f you don't crimp them you pretty sure not to get any split necks and etc..Some have onlt been resized 1 time is all..Fired formed cases sometimes are the very best to use..I will be sure to report my results....Johnny