Standard Issue was 40 rounds per man. This is what their Cartridge boxes would hold.

However, Ammunition was issued packaged in paper packets of 10 rounds and 12 to 14 caps. These packets were issued from wooden ammo boxes of 1,000 rounds.

In some cases to aid in the necessity of reissueing ammunitionn during the battle the regimental quartermaster would issue one or two of these packets extra to the normal 40 rounds.

Therefore if expecting a Major engagement soldiers would carry as much as 60 rounds per man.

And interesting note, The soldiers were trained to be able to fire 3 to 4 rounds per minute. If engaged in a hot fight this means that a trained soldier could empty his 40 round Cartridge box in as little as 10 to 15 minutes of fighting. That meant that the regiment would have to be withdrawn after that time to be reissued ammunition. Or the Quartermaster would have to bring his pack train or wagons forward to reissue ammo to the regiment. Hence the issuing of the extra packets of ammo in some cases.