This is a mag in handle smg nerf gun, fully printed, except for the motor components. It uses Jet Blasters' Katana mags, and shoots half darts.
It comes in many parts, that are screwed and glued together for the final product. Some filing and sanding is required to make sure everything operates smoothly.
https://www.thingiverse.com/thing:2829154
The pusher system is here. As it is a remix of other's better work, I didn't want to put it here, where it couldn't be credited easily.
The parts you'll need are:
Screws that fit nerf guns
Short, but strong extension springs. like 1/2" short, and small.
https://www.etsy.com/listing/586495168/jet-katana-mag-2-pack-short-darts-only?ref=shop_home_active_1
https://www.etsy.com/listing/570978696/xt-60-connector-male-2x?ref=shop_home_active_30
https://www.etsy.com/listing/568847863/mtb-neo-rhino-130-motor-for-nerf?ref=shop_home_active_46 (or similar high power, high torque motors)
https://www.etsy.com/listing/559995358/worker-short-darts-stefan-50-pack-3?ref=shop_home_active_58
https://www.etsy.com/listing/569816491/worker-high-crush-flywheel-set-abs-black?ref=shop_home_active_64
https://www.etsy.com/listing/569808257/plastic-gear-motor-yellow-3-6v-dual-axis?ref=shop_home_active_77
https://www.etsy.com/listing/567272865/18-awg-hobby-wire-fine-strand-5-red-and?ref=shop_home_active_81
https://www.etsy.com/listing/551274189/ofp-stryferapidstrike-nerf-flywheel-cage?ref=shop_home_active_95
https://www.etsy.com/listing/517700308/21a-microswitch-genuine-omron-v-212-1c6?ref=shop_home_active_21
And I think that about covers it.