Newest versions of the Stience. 17 and 20
17 is a short (80mm barrel) version and comes without a lampcutout.
20 is the newest version of the fullsize. Barrel is redesigned so you could also put a much longer insert in it. for example one that shoots a short crossbowbolt from a spigot.. ;) (stay tuned folks)
the breechlock with the single hexagon cutout should be a lot comfier depending on how strong your lock-spring is. 
But also it's a lot uglier than the one with the smaller (and grip-matching) hexagons.
Printadvise regarding the breechlock: print it laying flat on the underside with snug supports switched on.
the buildingguide is still valid in my opinion, yeah there are some changes but mostly in the design not in the function or placement.
as allways: happy printing and mass accellerating
LBRY Tags: printing; 3d2a; prototyping
Yah3D Mini Chemlight Magazine
                .75-16 to .5-28 Adaptor