Gorgeous work, fuck i haven’t got enough time myself to get back at realistic gun modelling 
Btw did you have any particular problem when modeling to match your reference? Like trying to match the perspective using a base reference and aligning the blockout, how do you accomplish this technique these days without eyeballing things most of time? For example this one of my models i
ended up abandoning because i ended up missing some shapes in the design and which also complicated the topology because i would had to remade that as well in some parts that i should have redone/correct according the design (even though it looks almost identical to the reference but it still failed is some areas, and also made this when learning advance d subdiv modelling 3 years ago so the topology was somewhat good, and other parts where some kind of disaster 
) SigSauer P226 X-Six 3D Model