Ah yes, the delightful 'Black Beauties'......I tried those years ago, based on Michael's (LeisureGuy) recommendation. Yeah, and he's not the only one who likes those black bloodsuckers. I believe the first two downward strokes were enough to see what a bad fit these things were for me. I think I mighta even stuck another of the same blade in my razor, to make sure I didn't get a dud. Those are a brutal little blade.
You know, I'd bet it was pretty tough shaving with a DE before 1965 or so. Up till then, all the DE blades were carbon and most likely gave a rough ride no matter what the brand. I'd guess it wasn't until Wilkinson came up with stainless steel blades that the shaves became more comfortable. Gillette followed soon after.
Martin