>>606594
lurk moar, but I'll indulge you anyways because I'm at work and have nothing to do.
>Submachine Guns
I'll lump PCCs in here as well (Pistol Caliber Carbines if you're a super newfag). These are really only viable anymore if they're compact-ultra compact, because otherwise why not just bring a carbine instead? Barring >>606599 and his comments, however, an SMG or PCC is really only practical if you have the following information
<Is the target wearing body armor?
<What is the proximity of your engagement? If it's closer than 30m, the SMG/PCC is ideal. This includes:
-being used for vehicle crews which may have to fight threats approaching the vehicle
-being used to defend VIPs or other high priority assets that are within the confines of a room
-fighting door-to-door in CQC
Outside of these roles, SMGs and PCCs are largely overshadowed by carbines
>Machine guns
I'm assuming you're referring to belt-fed machine guns like M249s, MG-42/MG3s, PKMs, etc.
These kind of machine-guns are generally known as light or general-purpose machine guns (LMG and GPMG respectively). They're best used in two distinct roles that are very different from each other:
<Suppressive fire: In this role, the MG will be used to prevent a foe from moving to engage friendly forces. You're not looking to make hits, but very close misses (as close as you can get them). This will make the opposing force (OPFOR) keep their heads down and give friendly forces (BLUFOR) an opportunity to maneuver to better engage the threat.
<Area Denial: This builds off of the previous concept of suppressive fire but to a much broader extent. Area Denial means that any OPFOR that crosses the line-of-sight from that MG is in what's called a "Kill-zone". In an Area Denial role, the MG will be set up in such a way that it's much more accurate than when it's generally used in suppressive fire. Sometimes that means affixing a bipod to fire it from, sometimes that means building a dedicated emplacement for it to fire continuously from, leading to much higher effectiveness of the Area Denial. MGs used this way will typically be operated by teams of 2-3 guys.
>Assault rifles
>Carbine (rifles?)
There doesn't really seem to be a difference anymore between the two. Before, a carbine was a long gun chambered in an intermediary cartridge that differed substantially in ballistics from the rifles that were standard issue. Assault rifles by and large are chambered in carbine/intermediary rounds and perform the same function but with much higher efficiency than their older predecessors. These are best used as a general purpose weapon, and can fill pretty much every role in the list without much trouble.
<Can be used in CQB situations
<Can be used to suppress OPFOR combatants, with modification can be used to act as ad-hoc area denial
<can be used as a marksmans weapon with the correct setup
>Scattergats w/ buckshot
Unarmored targets out to 75m. Outside of this range, the scattergat is largely useless. It can absolutely eviscerate an unarmored man-sized target out to about 25m, and at 75m you're looking at about 1-3 projectiles hitting their target with the same effectiveness as getting hit by a .45 at that range. Not bad, but could definitely be better. Most tube-fed shotguns are hindered by their slower reload times, while the mag-fed shotguns are hindered by their gigantic magazines for anything more than 5+1 shot capacity.
>Scattergats w/ Slugs
Lightly armored targets out to about 25-50m w/o optics. Effective out to about 150m with optics. Mostly though, the slugs are only good for big fucking animals. If you need to take out targets at range, you should go for an assault rifle.