If you want range and accuracy, it's the Rifled Musket. Very, very accurate, reasonably powerful, takes a week to reload. It's your quintessential sniper rifle, basically.
If you want a good balance of speed and power, it's the Jager Rifle. Not quite as accurate as the Rifled Musket, but more powerful, and quicker to reload, The jager rifle is easily the best volley musket in the game.
If you want to carry one weapon and 3 units of Cartridges for long fights, neither of these are ideal as neither one has a bayonet, and you should use the Charlville Musket w/bayonet, which is the most accurate standard musket and IIRC reloads slightly quicker than the Long Land Pattern musket (AKA the Brown Bess) which is the other good bayonet musket. IRL it was a lighter caliber piece, which is what I think that number is reflecting.
Be aware that I don't think you can move while loading the Charlville Musket, unlike the two rifles.