[Paddy] ''Griffith notes:
Even in the noted "slaughter pens" at Bloody Lane, Marye's Heights, Kennesaw, Spotsylvania and Cold Harbor an attacking unit could not only come very close to the defending line, but it could also stay there for hours — and indeed for days — at a time. Civil War musketry did not therefore possess the power to kill large numbers of men, even in very dense formations, at long range. At short range it could and did kill large numbers, but not very quickly.''
Also Grossman adds:
''Griffith estimates that the average musket fire from a Napoleonic
or Civil War regiment firing at an exposed enemy regiment at
an average range of thirty yards, would usually result in hitting
only one or two men per minute!''
Our previous count fits to his observation more or less. A regiment is about 1000 men, five times more then our 200 which killed 0,16 in a minute. Multiply this and we get 0,8 men per minute. However our closest distance was 70-75 m, Griffith calculated with about 30 (which I think would be the closest range, the next step would be a "Fit bayonets!" order and a charge). Let's say on that range our 200 would kill double amount: 0,32. Then 1000 would kill (or wound actually) 1,6 which a rough equivalent of 1-2 men per minute.

Bad visibility but on even closer range:
Sometimes the fire was completely harmless, as Benjamin McIntyre observed in his firsthand account of a totally bloodless nighttime firefight at Vicksburg in 1863. "It seems strange . . . ," wrote McIntyre, "that a company of men can fire volley after volley at a like number of men at not over a distance of fifteen steps and not cause a single casualty. Yet such was the facts in this instance." The musketry of the black-powder era was not always so ineffective, but over and over again the average comes out to only one or two men hit per minute with musketry.