Yes,

The Soper rifle - actually quite an ugly action, with the fame of being able to be operated very rapidly, the shooting was usually done by Soper's trick shot, Sgt. Warwick.  Technically, it is a Snider variant, sidelever-operated.   One of the reasons for its speed was that once the cartridge was in the chamber, pulling the trigger would close the breechblock and fire the shot in a single operation...  Pushing the sidelever down smartly would open the action and eject the case, and cock the hammer.  And as sidelever and trigger were conveniently close to gether, the shooter had a hand free for loading.

And another view.

"One of the reasons for its speed was that once the cartridge was in the chamber, pulling the trigger would close the breechblock and fire the shot in a single operation..."

Having not handled or examined a Soper personally I cannot say one way or the other regarding the above statement. However, Sherman Bell, in an article published in the Winter 2005 issue of THE DOUBLE GUN & SINGLE SHOT JOURNAL, after examining, and shooting three sporting Sopers made the following remarks: ""The rotating breech block contains the firing pin and a transverse locking bolt that holds the breech block closed until the rifle is fired, or purposely opened. The bolt also has a shoulder that blocks the firing pin from moving forward until the breech is fully closed and the side lever is raised fully to lock the block in battery." Maybe the trick shooter had a modified version.

The Soper IS HOMELY and somewhat complicated. It was presented for trials in 1868 but apparently was not considered for adoption. It was contemporary with the Snider and MAY have been a variant but with the breech blocking dropping into substantial recesses must have been much more robust. The three sporting Sopers featured in Bell's article are to my eye, in spite of the homely action, quite attractive rifles. This was the second Soper design, the first being the lever-actuated striker-fired falling block depicted in one of the links above.