I have been reloading ammunition for awhile, and reading all the threads on this site for awhile, and I keep seeing references to the "LEE Factory Crimp Dies". What are they for and what makes them different from all the "normal" die sets I have including RCBS, Hornady, Pacific, Lyman and Redding. Is there any advantages to a "LEE Factory Crimp Die"? How do they work differently than all of the other makes of dies? I don't see any of the other makers producing "Factory Crimp Dies", so is it not very important or doesn't really add to accuracy? Most of the ammo I have seen produced by the manufactures recently have crimps that look just like the die sets I have?