Fixed barrel springers, will there ever be a better setup than the sliding breech

[Hsing-ee]

Only problem is that it is not a fixed barrel

I have been studying the pictures and thought, no, they CAN'T have made it with the barrel sliding back and forth with all the slop that would imply, yet it cannot be a sleeve as that would mean about 10ccs of dead space between the transfer port and the breech... so you are telling me IT IS a sliding BARREL like a flippin Crosman M1 BB gun? Oh very dear me. First Webley-style trap-doors, now this.