It was an S&T airsoft, with the airsoft functionality removed and replaced with electronics.
It was a surprisingly straight-forward build, not going to say "simple", still challenging, but everything fit very nicely in their assigned locations. The BC, screen, and bargraph are in the ammo counter, the battery pack is in the grip, recharge port and first speaker are in the scope, and the main LED and second speaker are in the main body. ... Not a bad project if you want to spend the cashish for an airsoft and BC.
I also made it sound like a pulse rifle from Aliens. For those who have asked, please feel free to share!