iozjik

Seems like you a bit overestimate chest-mounted position for your phone. I've tried to design and print this type of phone holder. It takes a lot of place on your platecarrier, non-waterproof (so you have to put phone away during rain), camera may be damaged by BB. You also may damage phone by your gun while falling or going prone. And screen is poorly readable on sunny days, so you have to turn away from sun (and sometimes, enemy). So I recommend thinking twice about ordering this thingie. It may be a nice toy if you have 3D-printer (then you'll print it for 3$), but it will be much more disappointing to pay 50$ for it. 🤑

I use self-designed core-XY scheme printer. But this model adopted to usual 20x20cm heatbeds, so almost any modern printer may print this one. My first 3D-printed gun was made on Prusa Mendel and it was ok 👍

It already has 455mm barrel, so making gun longer is not too necessary. Anyway, silencer may be installed to cover longer barrel, but threaded part for it can not be printed, only machined =( I'm designing my new project now, so I'll consider designing longer version too 👍

Airsoft electric gun with custom 3d printed gearbox. Uses TM-compatible parts for gearbox v3 and m-series mags. Barrel length 455 mm. For extra toughness of construction used 10x20 mm alluminium channels. Gearbox tested with 148 m/s (487fps) output and works well. Gun is open-source, files may be downloaded on Thingiverse: https://www.thingiverse.com/thing:2916390