"A compact, wide-caliber slug-thrower. Very short range, but it packs a punch and handles quite well."
Added in Alpha 9. Similar to the PDW, but hits much harder.
The Heavy SMG is a moderately powerful weapon; with damage twofold of that of the Machine Pistol, and could almost be considered a side-step of the Pump Shotgun. In terms of overall profile; it could be viewed as a poor man's Charge Rifle - with similar overall cooldown periods, slightly less damage, less accuracy, less range, and relative ease to obtain. Heavy SMGs will generally be encountered mid-game - as pirates and outlanders transition from Machine Pistols and other low-tier weapons to Assault Rifles, and even Charge Rifles in the former's case.
Despite this difference however, the Heavy SMG is still not a weapon to be underestimated, as one wrong shot on an unarmoured colonist can still handily destroy their brain, or render lesser-armoured colonists as vegetables (unless they develop Trauma Savantism). It can also only take a couple of quick bursts to severely hinder somebody, or even kill them.
The Heavy SMG seems to take it's appearance after that of the TEC-DC9 Semi-Automatic Pistol in real life, albeit Full Auto in RimWorld. The Intratec TEC-9, TEC-DC9, or AB-10 is a blowback-operated semi-automatic pistol, chambered in 9×19mm Parabellum. It was designed by Intratec, an American offshoot of Interdynamic AB. The TEC-9 was made of inexpensive molded polymers and a mixture of stamped and milled steel parts. The simple design of the gun made it easy to repair and modify.