The initial variant suffered from numerous shortcomings: it could only engage targets flying at relatively slow airspeeds and low altitudes and then only from rear hemisphere, it suffered from poor guidance reliability (particularly in the presence of natural or man-made background IR radiation sources), and even when a hit was achieved, it often failed to destroy the target.
Poor lethality was an issue especially when used against jet aircraft: the hottest part of the target was the nozzle behind the actual engine, which the missile therefore usually hit – but there its small warhead often failed to cause significant damage to the engine itself.

In order to address the shortcomings, two improved versions were ordered in 1968; as an intermediate stop-gap the slightly improved 9K32M "Strela-2M" (NATO reporting name SA-7b) to replace the original, as well as the more ambitious Strela-3.

As the modifications introduced with the Strela-2M were relatively minor, the process was fast and it was accepted in service in 1970.
The Strela-2M replaced the Strela-2 in production lines immediately.
Improvements were made particularly to increase the engagement envelope of the new system:
Higher thrust propellant increased slant range from 3.4 to 4.2 km (2.1 to 2.6 mi) and ceiling from 1.5 to 2.3 km (0.93 to 1.43 mi)
Improved guidance and control logic allowed the engagement of helicopters and propeller-driven aircraft (but not jets) approaching at a maximum speed of 150 m/s (490 ft/s; 340 mph)
Maximum speed of receding targets was increased from 220 to 260 m/s (720 to 850 ft/s; 490 to 580 mph)
More automated gripstock provided a simplified firing method against fast targets: a single trigger pull followed by lead and superelevation replacing the separate stages of releasing the seeker to track, and launching the missile (see description below)
Contrary to what was at first reported in some Western publications, more recent information indicates that, while lethality on impact had proven to be a problem, the warhead remained the same 1.17 kg (2.6 lb) unit (including 370-gram (13 oz) TNT charge) as in the original.
This remained the warhead of all Soviet MANPADS up to and including most 9K38 Igla variants; to address the problem of poor lethality, a more powerful HE filling than TNT, improved fuzing, a terminal maneuver, and finally a separate charge to set off any remaining rocket fuel were gradually introduced in later MANPADS systems, but the original Strela-2/2M warhead design of a 370-gram (13 oz) directed-energy HE charge in a pre-fragmented casing remained.

The seeker head improvements were only minor changes to allow better discrimination of the target signal against background emissions.
Some sources claim that the seeker sensitivity was also improved.
The only defence against infra-red countermeasures remained the seeker head's narrow field of view, which could be hoped to help the rapidly slowing flare fall off the missile field of view as it was tracking a fast-moving target.
In practice, flares proved to be a highly effective countermeasure against both versions of the Strela-2.

The seeker is commonly referred to as a hot metal tracker.
The seeker can only see infrared energy in the near infrared (NIR) spectrum, emitted by very hot surfaces only seen on the inside of the jet nozzle.
This allows only rear-aspect engagement of jet targets, earning the weapon its other moniker as a revenge weapon, since the missile has to "chase" an aircraft after it has already passed by.

The Strela-2M was also procured for use on-board Warsaw Pact warships; installed on four-round pedestal mounts aboard Soviet amphibious warfare vessels and various smaller combatants, the weapon remained unchanged, but was assigned the NATO reporting name SA-N-5 "Grail".
The initial variant suffered from numerous shortcomings: it could only engage targets flying at relatively slow airspeeds and low altitudes and then only from rear hemisphere, it suffered from poor guidance reliability (particularly in the presence of natural or man-made background IR radiation sources), and even when a hit was achieved, it often failed to destroy the target. Poor lethality was an issue especially when used against jet aircraft: the hottest part of the target was the nozzle behind the actual engine, which the missile therefore usually hit – but there its small warhead often failed to cause significant damage to the engine itself.
In order to address the shortcomings, two improved versions were ordered in 1968; as an intermediate stop-gap the slightly improved 9K32M "Strela-2M" (NATO reporting name SA-7b) to replace the original, as well as the more ambitious Strela-3.
As the modifications introduced with the Strela-2M were relatively minor, the process was fast and it was accepted in service in 1970. The Strela-2M replaced the Strela-2 in production lines immediately. Improvements were made particularly to increase the engagement envelope of the new system:
Higher thrust propellant increased slant range from 3.4 to 4.2 km (2.1 to 2.6 mi) and ceiling from 1.5 to 2.3 km (0.93 to 1.43 mi)
Improved guidance and control logic allowed the engagement of helicopters and propeller-driven aircraft (but not jets) approaching at a maximum speed of 150 m/s (490 ft/s; 340 mph)
Maximum speed of receding targets was increased from 220 to 260 m/s (720 to 850 ft/s; 490 to 580 mph)
More automated gripstock provided a simplified firing method against fast targets: a single trigger pull followed by lead and superelevation replacing the separate stages of releasing the seeker to track, and launching the missile (see description below)
Contrary to what was at first reported in some Western publications, more recent information indicates that, while lethality on impact had proven to be a problem, the warhead remained the same 1.17 kg (2.6 lb) unit (including 370-gram (13 oz) TNT charge) as in the original. This remained the warhead of all Soviet MANPADS up to and including most 9K38 Igla variants; to address the problem of poor lethality, a more powerful HE filling than TNT, improved fuzing, a terminal maneuver, and finally a separate charge to set off any remaining rocket fuel were gradually introduced in later MANPADS systems, but the original Strela-2/2M warhead design of a 370-gram (13 oz) directed-energy HE charge in a pre-fragmented casing remained.
The seeker head improvements were only minor changes to allow better discrimination of the target signal against background emissions. Some sources claim that the seeker sensitivity was also improved. The only defence against infra-red countermeasures remained the seeker head's narrow field of view, which could be hoped to help the rapidly slowing flare fall off the missile field of view as it was tracking a fast-moving target. In practice, flares proved to be a highly effective countermeasure against both versions of the Strela-2.
The seeker is commonly referred to as a hot metal tracker. The seeker can only see infrared energy in the near infrared (NIR) spectrum, emitted by very hot surfaces only seen on the inside of the jet nozzle. This allows only rear-aspect engagement of jet targets, earning the weapon its other moniker as a revenge weapon, since the missile has to "chase" an aircraft after it has already passed by.
The Strela-2M was also procured for use on-board Warsaw Pact warships; installed on four-round pedestal mounts aboard Soviet amphibious warfare vessels and various smaller combatants, the weapon remained unchanged, but was assigned the NATO reporting name SA-N-5 "Grail".
9K32 Strela-2