It's finally done and I test fired it a few times to see how quiet it was. I still can't believe just how silent it is! It blows my mind and I think it may be quieter than my VSR, but I'll have to test them side-by-side this weekend to confirm that. I'm so happy so far and looking forward to obsessively tuning it this weekend and I'm hoping to be hitting out to 60m accurately. Targeting 1.14J on .32s with maximum effective range and maximum air efficiency.
And yes, that's a long line coming out of the stock, as I will put the tank in the stock pouch, though I do have a line and larger tank that I can use if I need. I think this might be my magnum opus airsoft sniper rifle build. The worst part about this is the quality of my camera, because my phone is about 5 years old