Small base dies are good insurance against that one round that might fail to chamber at a really bad time. The use of mixed brass and multiple rifles greatly increases the odds of such an occurrence, as do dirty chambers from high volume firing. Most die manufacturers offer SB sizing dies for rifle calibers that might be used in auto loading rifles. I started out loading for auto loaders many years ago with standard FL sizing dies. My experiences have demonstrated to my satisfaction the need for the SB dies in these applications. The experiences of my fellow shooters has reenforced my choices. My advice to those who choose to use standard sizers for auto loaders, adjust the sizing die to cam over at the end of the stroke, and use a chamber gauge to check loaded rounds. Eventually these steps will save you grief. None of this is conjecture, it's based on first hand experience and observations over 50 + years of shooting and reloading. I have learned not to gamble with my match and business ammo. It's an individual choice. Enjoy your AR!
Savage