The 9mm submachine gun is a small, yet capable weapon, able to empty a full magazine in under 3 seconds. The 9mm rounds don't deal as much damage as 10mm or 12.7mm rounds, but they're common and lightweight, making it even easier to spray-and-pray.
With the light bolt modification, this weapon deals an impressive 200 damage-per-second. However, it shares the common weakness of most automatic weapons in Fallout: New Vegas, in that much of its theoretical power is negated by the damage threshold system. In addition to losing much of its damage to the target's damage threshold, the high spread of the SMG requires the player to be at close range for all of the rounds fired to impact on the target.
Lucky 38 - a fully repaired one can be found inside the basement next to an ammunition box on a table. (Note: the player can only access the Lucky 38's basement when taken there by Mr. House during The House Always Wins, I or by console commands.