Good info. One thing to keep in mind about those RCBS small base dies... A customer of mine uses these for his Colt AR15, with 5.56 chamber, and is on the borderline of what I'd call excessive headspace. Those dies, in my opinion, would work best for an autoloading rifle with a .223 Rem chamber, as they are usually a tad tighter and have a shorter leade.
That being said, I know others who use the RCBS small base X dies for AR's and love them.
I've not tried the new line of AR specific dies RCBS is offering, the ones in the black box.. probably the same as the small base X dies, but with a new marketing angle.
I have a set of standard .223 Rem RCBS dies (full length), that I've loaded thousands of rounds with through my 5.56 chambered AR's, and love the loads they produce. Some people say that they (the regular FL dies) don't size down enough for autos, but my set sizes down nearly perfectly, I still have to back the die off about 0.04 - .06" to get the proper partial full length resizing that fills my chamber the best without being too tight.
The taper crimp die 264Winmag mentioned on the other hand, would be interesting. I shoot lots of BTHP match bullets in my AR's, without cannelures, so I don't ever crimp - and don't want to use a Lee Factory Crimp die, so the taper crimp die would be fun to test out... that being said, 9 times out of 10, crimping degrades accuracy, so I wouldn't crimp unless absolutely necessary.
