Building my first AR from scratch in 338 Federal. My first experience with that round was negative and I sold my brass and dies. Turns out it was a problem with the rifle, not the round.
So, when I reload for my 223 Rem I use small base dies.

I'm planning on trying the Hornady 185 GMX bullets to start.

I noticed that RCBS sells a 2 die set with a small base f/l die and a taper crimp seating die.

Your thoughts/experience?

Thanx,

GWB

I built one and used a standard 338 Fed reamer for the barrel (this was on an Armalite AR10). I don't remember any issues just using the two die set for loading, and I didn't crimp the ammo either. I don't think you will NEED the SB die, but if you do it's really not too much extra expense to ensure reliable cycling. Only way you'll know obviously is to shoot it with just FL sizing and see.

Small base dies are very rarely needed. The issue is not a small based chamber, it is base to shoulder LENGTH. I have had this happen many times (others rifles). Some FL dies won't make the brass short enough for AR chambers which have no camming closing power. They do not use small base reamers to chamber AR type rifles with.
So will a small base die help you? Don't bet on it, from my experience.

I have Browning autos in .243, 270 that I reload for, I use the same ammunition I shoot in my Winchester m70's... this go-round, all was full length resized... and no more than they get fired, i'll probably full-length resize next time too... I thought about the small-base dies for those, but didn't have any access to them, so I used regular rcbs dies...I haven't had any problems with either,,, yet,,,