I don't load from other associated cartridges for the simple reason that we do make mistakes. I've been reloading for 40 years and you can believe that all the cartridges that go into my .308Win. will have a .308 headstamp on the case, not .243, 260Rem. or .358. It doesn't have to be from tired old eyes, simply being tired will often have the same effect. I once fired a .222Rem. in my .222Rem. Mag. It didn't hurt anything except produce a wierd looking empty case, but it taught me something. Also I've noticed the newer cases aren't as clearly or deeply stamped, making it even harder. It's not all your eyes pal. Best wishes.