I've never seen this one before but I'll try to guess at how it was itended to work. The op handle is pushed forward which by a linkage under the barrel, tips the breech up, muzzle down. There's a breechbock attached to the carriage, and when the breech rises, the bore or chamber is uncovered since the breech is pulled off of it. Gun is loaded thru open breech, lever pulled back, breech drops down over breechblock, etc. A possibility anyway.