Heathaway MX175 semi automatic bb repeater from the 1960's
600fps bb semi auto repeater. Holds 100 rounds. 21.5 inch barrel 41 inch total length 4.5 lbs 8g or 12g co2 cartridge
They made a MC22 same gun with rifled barrel it used steal coated lead roundball ammo so the magnetic feed could pick it up, The ammo was specially made by them. The ammo is hard to find.
Both guns are rare. The MC22 more so.