Maybe a Kel-Tec Sub2000? Or a Hi-Point Carbine?
Pistol caliber and 4-5 pounds (for the Kel-Tec at least)
'A Vote is like a Rifle; It's usefulness depends upon the character of the User.'-Theodore Roosevelt
'In a Man to Man fight, the Winner is He who has one more round in his magazine.'-Erwin Rommel