The museum’s gun crew not only drills with that rifle, mounted on a naval carriage, but occasionally fires blanks from it:
The drill may look somewhat awkward, with a lot of folks just standing around. Only a couple of guys busy at the muzzle end? Keep in mind that drill was intended for a weapons station onboard a ship. The “open air” setting allows us to see all the work (heave!) done to get the gun into battery. But we lose the context of the cramped quarters on the ship.
Here’s another video, this one from the museum’s channel:
A considerable amount of the “flame out” is due to the blank cartridge. With a projectile, the internal dynamics would allow for more complete burning of the powder. Not all of it, of course.
Likewise the recoil is minor for a blank, having something to do with Mr. Newton.
One of the staff briefly discusses the composition of the blank round:
One of many reasons to make a stop at the National Civil War Naval Museum.