That is all well & good, but no army in the world converted from rifles back to smooth bores... or crossbows for that matter.And again with the listing of the number of results from a Google search.
Did you notice that the very first answer was "300 yards"?
Well, of course going from a smoothbore to a rifle is an improvement if you train your men - and to some extent even if you don't, because a few men will be good shots regardless. But if you can get one hit out of fifty on a realistic target it is exceeding the actual performance of the Union armies at Gettysburg.
But you and nine hundred of your friends standing in a line, and nine hundred people all shooting at you with smoothbore muskets? Ten volleys at a hit rate of one in two hundred and you've lost forty-five friends.
British experts quoted the battle range of the smoothbore Brown Bess as 200 yards, and as we've seen it could be used outside that range.
Now, as it happens I found an online source which actually shows the test cards in Fuller. What I'm going to do is to overlay a double line of infantry on the smoothbore ones, assuming that the men are 5 foot 8 inches tall (which is 17/18 of the total height of the 6 foot cards, and which is the average height of an adult American male as of the Revolutionary War - which is when I have data for it).
View attachment 357632
As you can see, at 100 yards the men are completely peppered. In fact, there are 17 hits on the legs, 12 hits on the body, and at head/neck height there are 9 balls which have a good chance of hitting.
So out of 50 shots fired here there are more than 30 hits (60%).
At 200 yards there are about 9 hits on the legs, 8 hits on the body, and 2-3 balls at head-neck height - so about 20/50 (40%)
At 300 yards, there are 4 hits on the legs, 2 on the body and 1 at head height. So 6-7 hits out of 50, or about 2 in 15 (13%).
Since 13% is still more than ten times as accurate as Union troops at Gettysburg, I would say that the theoretical accuracy of the smoothbore musket allows for the possibility of effective firing at 300 yards.
If you and 900 friends stood in a two-deep line 300 yards away from 900 men shooting at you with smoothbore muskets at this level of accuracy, each volley would hit more than 100 of you. I think I'll decline to join you...