Uh no, blanks look nothing like real rounds. Most are crimped, and it’s obvious there is no projectile in the cartridge. Perhaps you meant to say dummy round? Even those are easily distinguished from live ammo by the visibly obvious lack of a primer.
Older blank rounds particularly low pressure black powder era rounds can and do have cardboard and wax sealed fronts that are flat and look very similar to wad cutters of the same era rimmed shells. Crimps are to keep same over all outer dimensions so semi automatics will feed them from a magazine. Those are actually more dangerous to shoot at someone since it’s not uncommon for a petal or two to come off and shoot out the end of the gun. Thin paper and wax is disintegrated by the heat and pressure. This is the reason in the service before they went to blue.sim rounds you.never shot blanks directly at someone.
You and I are familiar with the same thing with respect to dummy rounds and their empty primer pocket or orange/yellow fake plastic primer. I was surprised at the beginning of this shooting fiasco that pictures of what looked like cartridges with metal (fake?) primers and a hole drilled in the side of the case were being shown. With what you and I are familiar, one could easily see if the loaded cartridge was a dummy or not. With a dummy round that can only be checked by looking at a hole in the side of the case, one would have to remove each round to check.