In one review the author noted that his infantry started with 20 rounds each. That was British standard for premade cartridges at one point in time.

However, he also said something about it being increased with a tech and I have gone on about simpleton technologies as a result of that interview.

I know that one special unit (Roger’s Rangers) had standing orders to carry 60 cartridges plus powder and shot so I don’t know how much you can work up to for musket and rifle men.