Originally Posted By: MGYSGTNothing wrong with small base dies. Yes, they ensure flawless functioning in the AR. Some chambers are just too tight. It doesn't hurt anything to use small base dies.
they may not necessarily hurt anything as far as performance goes, but they may lead to shortening your brass life a bit.
by their nature of sizing down to minimum specs they're working the brass harder than a standard FL sizing die would. there's the potential see more neck growth (that brass has to flow somewhere), require more trimming and likely have case-web separations or neck splits earlier.
I have SB dies on my bench, but i've yet to find a chamber on one of my guns that needs them. i only use them for first time sizing brass that my regular FL dies wont resize properly so they fail a sheridan gauge (which is cut to minimum chamber - which is just larger than maximum cartridge dimensions). this so far for me has only applied to once fired MG brass - raw military stuff on its first processing. Kind of like swaging crimps out of the primer pockets. Otherwise they're pretty lonely there in their boxes.
Generally speaking if you can size to pass a sheridan gauge - unless you have an EXTREMELY tight chamber - you should be more than fine chambering in your rifle with a good quality FL die for everyday use.
if i had to guess why midway sells the SB dies cheaper - its because they're much less commonly used, but thats pure speculation on my part.
hth