OK, the information in this post will be aimed more at making pouches more HC/PC. If you are not concerned with doing this, then feel free to ignore these suggestions.
Many of us have made shot pouches for use with 18th century guns and those pouches included details that were not common or not even known until the 19th century. Yep, have to admit I was guilty of that a couple times myself. :redface: Now, it is not a problem when one is reenacting the early or later 19th century when those details were known or common for shot pouches then, while still using an 18th century gun.
Something that was at least extremely uncommon, if not unknown, for 18th century pouches was to use "O" or "D" rings on the straps. Now on some 18th century Fowling Pouches, they used some interesting metal hooks and rings, but not "O" or "D" rings.
The next thing to keep shot pouches HCPC is if one uses buckles or other hardware, to make sure they are correct for the period the shot pouch is supposed to represent. For the most part, buckles available from places like Tandy are not HCPC for many period shot pouches. Some few can be modified to be correct, but one has to study the different hardware used in the different periods. You CAN find period correct hardware for almost any kind of pouch you want to make, but you have to look more to find such hardware.
This suggestion is more complicated and I hope I don't mess up while trying to explain it. IF a person or customer is interested in an HC/PC shot pouch, then I feel it is a good idea for the shot pouch maker to learn as much as possible about the persona the customer is doing. For example, a poor farmer or frontiersman would almost certainly not been able to afford a shot pouch made by a Saddler or other professional leather worker during the period. So when making a pouch for someone doing an impression like that, try to keep it as simple as possible to be HC/PC. Of course, a young person may have inherited or been given a more expensive shot pouch, though.
My last piece of advice for this post concerns fitting the shot pouch to the customer or the person you are making the pouch for as a gift or trade. I ALWAYS prefer to put the strap/straps on the person's body and cut the strap to length that way and mark on the pouch the angle for the strap ends that will fit the person best. Of course some original pouches had straps sewn on straight, but the strap/s fit better when they are angled outward on each side. BTW, this really gets important if you ever make over the shoulder bayonet and sword slings and/or waist belt frogs for either.
Gus