Both the grenadier and rifleman are dressed for the Napoleonic period in game. By that time nobody used grenades any more as musketry had gotten good enough that it would have been suicidal. Really grenades shined in the period where they could reach out about as far as the average musket and that means the matchlock era. By the early mid 18th century once you get decent flintlocks everywhere they disappear. And from than on it's basically just really big burly guys with cool beards to scare the enemy into retreating. So depending on how you look at it either the in game grenadier is dressed wrong and should look and be in line time vise with the musketeer unit rather than the rifleman or he is dressed and placed right in the tech tree but should have a musket. Or you can be like me and just accept with a smile that the makers of CIV4 made the best ruling from a rule of cool perspective and be happy that they did.