The Spectre M4 is a submachine gun manufactured by SITES (Società Italiana Tecnologie Speciali S.p.A.) that chambers several different calibers. These calibers are the 9x19mm Parabellum, 9x21mm IMI, .40 S&W, and .45 ACP.Note: The Rainbow Six universe refers to the Spectre as the SM4 CQB. The weapon was later renamed the SP M4 in Lockdown. This does not count as a different variant of the weapon.
Tom Clancy's Rainbow Six 3: Raven Shield
The SM4 CQB is a weapon featured in Tom Clancy's Rainbow Six 3: Raven Shield.
The SM4 CQB was designed in the mid-1980s with a focus on bringing a lot of power to bear in CQB situations. A recoil-operated automatic firearm, it has a unique trigger design that more closely resembles that of a SMG than a pistol.
Tom Clancy's Rainbow Six: Lockdown
The SP M4 is a weapon featured in Tom Clancy's Rainbow Six: Lockdown.