Which RPG variant does not have a long service life in the Soviet Union?

The RPG-16 is the correct choice because it was a less successful design compared to other RPG variants, resulting in a limited production run and thus a shorter service life within the Soviet Union. The RPG-16, which was developed in the 1960s, had some innovative features but was ultimately overshadowed by the more versatile and widely adopted RPG-7, which became the standard anti-tank weapon for Soviet forces.

In contrast, the RPG-7D and RPG-7 Iranian variants benefited from the enduring popularity and adaptability of the RPG-7 platform, allowing them to remain in service for extended periods. Meanwhile, the RPG-22, though a different design, still enjoyed a longer operational history due to its effective development and deployment, further contrasting it with the RPG-16’s limited service.

The focus on other variants and their successful integration into Soviet military strategy elucidates the RPG-16's relatively brief service life in comparison.