A section was the smallest organizational structure in the Soviet Army. It was present in every branch of service and would usually correspond to the single vehicle crew or a number of foot mobiles.
Since we are focusing on the infantry section here, we will discuss the organizational structure, weapons and equipment of the most regular and common Soviet Mechanized infantry section.
Different types of section in different branches
As was said in the introduction, every branch of service had its own organizational structure of the section. Given that a given infantry unit would never exist on its own, but instead was a part of a bigger structure, like a regiment or a division, it is wise to go over section structures of some other branches of service.
For the tank troops, the typical section consisted of just three man - the crew of the late cold war tanks, such as T-62 and T-72. This crew sized section was lead by either a sergeant or an officer. The officer would also be in charge of the whole tank platoon or even a tank company, depending on his position.
Similar structure was adapted by the artillery or communication troops. The section was of the size of the number of people assigned to the given piece of equipment.
Soviet infantry section battle order on BTR
During the Soviet Union's existence, the organization and structure of its infantry section changed several times. It is unclear of how the sections were organized in the postwar environment of 1950s and 1960s. However, after the introduction of modern APCs and IFVs, the section size became dependent on the amount of people which could fit in a single vehicle. Since the introduction of the BTR-60P, the typical soviet infantry section would consist of the vehicle, it's crew and armed passengers.
So, the section armed with the BTR-70 would consist of 8 foot mobiles and 2 crew members. The configuration of the BTR-80 has changed a little, so that the number of crew members increased to 3 and the number of passengers decreased to 7. However, the third crew member was the section commander and he could operate on the ground if this was required by the situation.
The BTR-60P setup is a bit unclear, as well as with any older vehicles, such as BTR-152 or BTR-40. The number of people that could be fit to BTR-60P is 14 passengers and 2 crew members. However, the sections in the Soviet Army were never as huge. It is possible that at the time there were only two BTR-60P per platoon.
Soviet infantry section battle order on BMP
In the middle of 1960s the new vehicle was developed for the Soviet ground troops - the BMP-1. This vehicle featured a 73mm main gun, a PKT machine gun and ATGM rockets. All in all, this set up increased the firepower of a single infantry section by a mile.
The section setup was relatively similar, due to the similar number of passengers per vehicle. Both BMP-1 and BMP-2 had 3 crew members and 7 passengers. And again, the 3rd crew member was the section commander, who would usually operate on foot after his section was dismounted.
Apart from that, infantry could, in theory, operate on other means of transportation, such as MTLB or trucks. There is no documents in open sources of what should be the battle order for such set up. But all in all, it is safe to assume that in any given time, the number of foot soldiers per section was supposed to be eight people.
Roles in section and their weapons
This is an idealistic table setup for the infantry section battle order. It could and would vary depending on numerous factors.
Vehicle gun operator
*GP-25 could be issued, subject to availability **Grenadier would typically carry just an RPG-7 during training, without the PM. Ironically, during the actual war, he would carry a rifle, but still no PM.
***One AKS-74 rifle was stored in the fighting vehicle
Motorized Rifle section setup by BattleOrder
Note, that this setup is correct for 1980s. Before that, and even during the 80s, infantry sections were armed with AKM rifles and RPK machine guns respectively. Also, the section could be equipped with some MANPADS. It would be either Igla-1 or Strela-1 launchers. They were stored in the vehicle and used when possible.
Everything described in here is an idealistic and idealized setup which never existed in practice. Even during peacetime, on a training exercise, not every soldier would be present, so the section would not be at its full power. The ranks could also be different, especially in war scenario. The section could be led by a warrant officer, and there could be no privates at all.
The number of people in the section at war could also be very different from what was required by the book. For example, in Afghanistan, due to combat losses, diseases, holidays and injuries, a given company would usually be around 30 man strong. Meaning that a given platoon was a section sized and sections would seize to exist.
Alternatively, in the case of a big war, vehicles would soon become rare and there would be more people on foot, without any transportation assigned to them. There would be lack of commanders, too. This mean, that sections would now have more people and could easily be 15-20 man strong, which would actually be preferable in both defense and human wave offensive.
Same goes for the weapons. The idealistic scenario depicted in the table would not and did not work in combat. Sections could easily get their hands on the weapons which they would actually need for the missions - e.g. get some SVDs, replace RPKs with PKMs, get AGS-17 etc etc etc.