Mk7 and others............ Why do the cases lengthen? You can only lengthen at/to the detriment of something else surely? And surely, if they DO lengthen, then lengthening in this context is simply stretching. And in that case they'd lengthen uniformly along the total length - yes?

As I said I'm not and never have been a reloader but.......... Maybe there's more Q's than A's in the reloading game!