May 12, 2020:
Iran has been under various arms embargoes since the 1980s and has become quite proficient at taking older vehicles and weapons and adapting them to new, and often unexpected, uses. Iran is not alone in this sort of improvisation and they encourage their allies to do the same. Iranian technical advisors are sent to pass on the knowledge, often with some tools and components brought in as well. A recent example of this was a picture of Iran-backed Shia rebels in Yemen using a captured American hummer vehicle with a BMP-1 turret and its 73mm cannon added to the top of the vehicle.
The BMP-1 is a 1960s era design. It is 13 ton armored vehicle with a cramped one-man turret armed with a 73mm low-recoil cannon and four ATGMs (Anti-Tank Guided Missiles). This turned the BMP-1 into the first IFV (Infantry Fighting Vehicle). This BMP-1 turret was always a source of user complaints but, when that turret was mounted on a truck or similar vehicle, those complaints went away. While the turret was not all that bulletproof it did offer some protection and was better at stopping shell fragments and similar debris flying around during combat. When not on a BMP the one-man turret did not require the vehicle commander, who often stuck his head and shoulders out of the turret to get a better view, to duck down inside the turret to operate the 73mm gun, which had a range of 4,500 meters and was pretty accurate, especially when using high-explosive shells.
The turret alone weighs about a ton and the usual armament, a 73mm gun, weighs 115 kg (253 pounds). The turret rotation uses 24-volt electric motors for traversing and raising and lowering the gun barrel. It is possible to improvise a slower manual rotation and gun movement system. While the cramped and thinly armored BMP vehicle was never very popular, the turret and its 73mm gun were. That 73mm gun was designed as an anti-armor weapon but by the early 1970s the Russians realized that it was more often used for infantry support and provided high-explosive rounds. These were a little heavier (4.5 kg/10 pounds) but much more effective against troops or structures. The 73mm gun had a 40 round magazine below the turret which provided ample ammo for combat.
There were other ways to improve the BMP-1 turret. In 2016 a Ukrainian firm modified its Shkval RWS (remote weapons station) to be used on older BMP-1s. That sort of thing takes these older vehicles that are still in service and makes them useful again. Since the 1990s Ukraine has prospered by providing refurbishment and upgrades for these older vehicles. One popular upgrade was the Shkval RWS, which was introduced in 2012 for more recent wheeled armored vehicles. Putting it on BMP-1s seemed like a good idea and it was. While Shkval weighs 1.9 tons, it allows the operator to sit below the turret and more easily handle the many weapons packed into Shkval. These include a 30m autocannon (with 225 rounds ready to fire), a coaxial 7.62mm machine-gun (with 2,500 rounds), a 30mm grenade launcher (with 29 rounds), two modern ATGMs and six smoke grenade launchers (using grenades generating a mist that confuses laser-guided missiles). Shkval uses a modern computerized fire control system that includes a weapon stabilizer. The operator has a thermal sight available as well as a laser rangefinder.
No one has yet tried to mount a Shkval on a hummer but that is an option because the hummer has used lighter RWS turrets that the U.S. Army bought with hummers in mind.