this Designs is from the original browboy BSTRD-10 Carbine: Shell Ejecting Blaster
https://makerworld.com/@BrewBoyBlastersToy semi replica 3D printed Carbine
Used that and added some minor modifications as:
threaded barrel
Separated all picatinny rails for easier print
Lower barrel cover extension
upper barrel cover slots.
added thread inserts
Added cavities For advanced users so we can add lead weight all over the model for more realistic - Feel
enlarged magazine, upper and Lower Mag housing to accommodate real size
9 mm shell .
changed the way upper and Lower are married
added A BRACE quick connect pin