How would an extended magazine for a Makarov work?
The Makarov's heel magazine release would be a problem, since an extended magazine would not be able to lock into place.
There were some hi-cap Makarovs imported several years ago. But, the magazines were not interchangable with the standard Makarov. The hi-cap Makarov used a double stacked 13 round magazine and the standard Makarov used a single stacked 8 round magazine.