Comparing the 243 win with the 6mm rem
Starting off I don't know either of these from an owners point of view. I have shot a 243 but never the 6mm rem. I do remember from my reloading manuals that the 6mm Rem case has a longer neck and is more reloader friendly than the 243 win. I think that I would rather have the 7x57 mauser or 257 roberts over the 6mm rem when using them on Deer. Just my opinion.