Shooting old military rifles at nicely manicured ranges on perfect sunny days is fun, but doesn’t really give us much useful information about how they were used in the context of battle. It is impossible to recreate the stress, confusion, exhaustion, and conditions that Civil War soldiers experienced on the battlefield.
The best we can do, as historical researchers doing experimental archaeology, is consider the actual weapon systems themselves, and how capable or incapable they were on their own, outside of any battle conditions. This is still useful information to obtain. For example, the US Model 1861 Springfield rifle, when using the historic load with the .574” bullet, is not capable of very good accuracy; the smoothbore easily holds its own against it out to 100 yards.
To what extent this influenced battle, or posed an advantage or disadvantage to troops armed with these guns, we can only make a very broad guess.