The LMG is a heavy, multi-shot firearm in RimWorld which fires a burst of 6 low-damage shots; has a slightly shorter time between shots in a burst; a slightly longer time between bursts; moderate range; and poor accuracy.
As a result of having a 6-shot burst - greater than most other weapons which typically have 3-shot bursts - alongside poor accuracy, the LMG's strength comes out more in small groups of tightly-packed enemies as opposed to individuals, although it's still somewhat competent at dispatching of individual targets. Its low accuracy also means that it's not recommended to use LMGs against smaller targets such as rats and alphabeavers, but it does benefit against larger targets such as boomalopes and grizzly bears.
Due to the LMG's longer time between bursts and its half-decent range, it's advisable to pair it with a competent shooter to properly utilise it. 97% is the minimum recommendable shooter accuracy to be looking for when seeking a decent LMG wielder, which can be achieved with a level 8 careful shooter; level 10 standard shooter; or a level 14 trigger-happy.
The LMG is one of the weapons of choice for elite mercenaries.
LMGs can be purchased from outlander combat supplier and towns, or from an orbital weapons trader - and LMGs can also be obtained from incapacitated outlanders, pirates, and mercenaries. LMGs can also be produced at machining tables once the machining research has been completed; for 75 steel, 4 components, and 34,000 (566.67 secs) of work.
Conclusion & Comparison
The LMG overall falls behind the slightly cheaper heavy SMG in terms of damage output and accuracy, but beats it in range. Therefore, it's considerably worse than the charge rifle too against single targets. However, that's not really the LMG's purpose (as touched on earlier); it can be objectively viewed as a compromise between the heavy SMG and the crowd-controlling king; that is the minigun - those missed bullets have to go somewhere. Still, it's superior to the machine pistol in terms of damage output beyond touch range.
In short: it's the chain shotgun of the machine gun world.