Hi friend,
Firstly, when talking about history, it’s never a good idea to take modern ideas as evidence for past actions or events- so “I do it this way” sorts of answers should be taken with a grain of salt. Secondly, when you say “they” and “back then” we could be talking about the 1950’s, the 1850’s, or the 1750’s.
My primary area of interest is the 18th century. While there are examples of 19th century internal ball bags, there is, as of yet, no verifiable evidence for such a thing in the 18th century. That doesn’t mean they didn’t exist, but in recreating something like that for 18th century-minded “reenacting” or “living history” etc., it is mostly conjecture. There are precious few examples of extant surviving shot pouches (hunting/shooting bags) with 18th century provenance, and none survive that were of the homemade variety (though a couple have been disputed as possibly dated to the 18th c.)
In Virginia, the shooting bag was often called a “shot” or “bullet” pouch. This gives us some idea as to what they used these for. Surviving examples and period artwork for this time frame depict smaller bags- smaller than what many folks typically use today. It seems reasonable that those smaller bags were intended to hold ammunition and not much else. There are references (as well as one surviving example in the Wallace Gusler Collection) to shot pouches with an internal divider for separating ball from shot. I think for now, for the 18th century, there is more evidence for shot pouches carrying loose balls than for separate bags within the main pouch. This differs from the 19th century, where there are numerous examples of internal ball bags and even loading blocks.
I find the safest way to emulate the era that I am most interested in is to carry loose balls in my shot pouch- this also makes it very easy to reach in and grab a RB.
James