Not that I'm ruling out the possibility that you had tolerance stacking that requires SB dies but in my experience the perceived need go SB dies tends to go away with proper sizing die adjustment
Why is it when someone says a small base die solved his problem, the predominant suggestion is that his original dies were set up improperly.
While die set up could be the issue, in my opinion is is not a common reason particularly if a person has been successfully reloading for a particular rifle.
There are situations where a small base die is necessary and admittedly, these are few but they are real.
Cases fired in one of my AR-15s and full length resized with a properly set up standard resize die will not chamber in a couple of my other AR-15s.
If the cases are segregated by rifle, they will chamber again in the rifle they were fired in without changing the adjustment of the sizing die.
Yet, if I use a small base die, no problems chambering any case in any rifle.
New cases and new ammunition work fine.
I use a small base sizing die with all my 223 Remington ammunition so that I do not have to segregate ammunition for each rifle.
What I have learned over seven or eight years of dealing with this issue is that if the cases were not fired in a particular rifle, there could be a chance that the cases resized with standard resize dies will not chamber in that rifle.