I don't know if there is any English language source that would tell us the precise loading of a Swedish musket in the 17th and 18th century, but it largely doesn't matter. The m/1704 musket was very similar to every other main line smoothbore infantry weapon from the invention of the flintlock in the mid 1600s to the invention of the Minie ball in the early 1800s. It fired a 20mm lead ball weighing about 500 grains (32g) with about 100 grains (6.5g) of blackpowder behind it. Typically, these lead balls are undersized compared with the bore to allow quicker loading. The resultant projectile had a muzzle energy of about 3-4000 joules. For comparison's sake, the modern 5.56mm NATO XM193 55gr loading fires a 55 grain copper-jacketed lead bullet at 1755 joules.

The obvious downsides of the 17/18th century musket is its accuracy and rate of fire. These muskets were smooth bore, had no sights worth writing home about, if any, and there was large variations of projectile weight and powder weight. You couldn't expect to hit anything you intended to hit beyond 100 yards, and contemporary doctrine fired at much shorter ranges. Swedish Ga-Pa doctrine, for which the Caroleans were famous, called for a first volley at 50 meters by part of the formation and then another at 20 by the rest, before charging in with rapiers, pikes and bayonets. Aiming was not a part of the procedure; you fired into the masses and if the god you believed in willed it and the god they believed it didn't, the bullet would find its mark.

A hit from a musket ball was devastating. It would tear a hole in your body about an inch wide, most likely clear through, and possibly into your mate standing behind you. However, what made the Caroleans feared by their contemporaries wasn't the deadliness of fast moving lead, but their previously mentioned doctrine. A coordinated volley at short range is extremely loud, and would cover the front of engagement with smoke, and while you are disoriented by the sound, the fury and potentially the gaping hole in your chest, the Swedes are all upon you with religious fervour and sharp sticks that you would very much prefer to remain external to your anatomy.

In summary, no more or less deadly than any other infantry weapon of the time, but you certainly wouldn't want to get hit by one.