"A compact, wide-caliber slug-thrower. Very short range, but it packs a punch and handles quite well."
The heavy SMG is a moderate-weight, automatic firearm in RimWorld which deals considerable damage, has a moderate-high fire rate, very short range, and moderate accuracy. Although the heavy SMG is limited strictly to close quarters combat, it is capable of doing this very effectively - although it is indeed no charge rifle in that aspect. As it's restricted to not far above the 'short' range threshold, the heavy SMG is a decent weapon to equip those with poor (less than 95%) shooting accuracy, while still performing somewhat decently.
The heavy SMG's main strength lies in its solid theoretical damage output.
Heavy SMGs can be purchased from outlander and orbital weapon traders for a low price, or obtained from outlander and pirate raiders predominantly in the early-mid game. Heavy SMGs can also be crafted at a machining table once the machining research is completed; from 45 steel, 3 components, and 28,000 (466.67 secs) of work.
Conclusion & Comparison
Overall, the heavy SMG is a very limited weapon, but it is a solid performer where it counts - primarily with its high stopping power. Although 13 damage per shot in an automatic weapon is an excellent amount - even edging out the charge rifle's 12; the heavy SMG is still let down by its comparatively long time between shots and comparatively poor accuracy, and these two areas are both where the charge rifle is vastly superior. In its class, the heavy SMG sits above the machine pistol, and is on par with the pump shotgun; but it falls significantly behind the LMG and the charge rifle.
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.