T-dolls can literally lift a truck. Sten has done that in canon and shes one of the weaker non main character dolls. To be exact, Sten punch'd a Jeep/car stoping it in it's tracks.
If i'm allowed to talk about main characters though. STAR15 hols 2 ARs in 1 hand each after her MOD with perfect accuracy, recoil be damn and SOPMODII is capable of cutting through concrete with her bare hands.
As far as "real weapons in the real world" are concerned. The answer to your question isnt usually weight. Its Recoil. Recoil is pretty much what's stopping most people from juggling guns around beyond movie magic Gun-kata stuff.