Except for the fact that a straightwall sizer isn't tapered, which negates the utility of using it as a taper crimp die. All it will do is swage the bullet in the case to a smaller diameter in a straight line. 9mms, with their extremely tapered cases might be an exception, but then there's not really enough angle to the taper to do you much good. Taper crimping only prevents bullets from being pushed back in the case during an autoloaders cycling. It's worthless for revolvers which normally require a roll crimp to prevent the bullets in a cylinder from backing out of the case due to inertia. Also, slower powders require a higher degree of resistance (bullet "pull") for consistent ignition. I've heard of some guys claiming that taper crimping wadcutters with fast powders makes the load more uniform, but I'm a roll crimp guy when it comes to revolvers. Since the die sets have a crimping die anyway, why not use it?