A Russian inventor has developed an eighty round 9x18mm magazine for the Makarov PM pistol. He writes (in Russian) that the Makarov is still in use by police in Russia not because they cannot afford new pistols but because the Makarov is genuinely loved. He says the problem with them is that standard magazine only holds eight rounds and extended magazines only hold up 12 rounds. Twelve rounds is not a lot by todays standards, especially when you consider that the 9x18mm is about 30% less powerful than a 9x19mm NATO. His solution was to develop a drum magazine that holds eighty rounds.
On a side note, the 9x18mm, despite being almost 50 years younger than the 9mm Luger/Parabellum, was intentionally designed to be anemic because the Soviet Army wanted a simple blowback pistol with a fixed barrel.
Many thanks to Val for the tip.