Fallout 3/NV's engine couldn't support a Chicago Typewriter, and that is why their wasn't one in the game. Honest Hearts had .45 ammo, .45 pistol, .45 Thompson smg, but not a Chicago Typewriter or 'Tommy Gun'. You could download a mod with a Tommy Gun obviously, but for what ever reason it was gimmicky to have foregrips. It could still be this way in Fallout 4, the only thing that breathe's hope is this concept art, Now their is not any actual real life gun models in Fallout 3 to my knowledge, and probably definitely won't be any in Fallout 4. Just to have that out their as a disclaimer. Their was obviously a lot of irl look alike gun models in New Vegas however. Their is a gun though in the F4 gameplay trailer that could come very close to a Tommy Gun. Add a drum, foregrip, and a compensator. Not that a Tommy Gun had a compensator necessarily, but it will complete the look and keep it classified in game as a SMG. The gun is obviously a smg, but can be modded into a rifle obviously too.