I wanted to know, how other slingers get their ammo.
Most of the time, i use the ammo at the spots i'm training at, but sometimes i collect some stones at a river, that is flowing through my town.

   Here in South Jersey we are just south of where the glaciers stopped at the end of the last ice age.  As they melted and retreated they put most of this area under water.  Consequently finding good ammo in the form of oval shaped white river stones is easy. They are everywhere.

Finland has some amazing round granite for the same reason Ratman described. Absolutely perfect slingstones. The problem is that most are under ground on the coasts of the islands. When they dug up around our area to change some pipes, I went through the dirt piles and picked out a load of stones. I've found a few other spots but it's all where soil is eroding away, has been disturbed or it's been moved.

Lakes sides and beaches. But mostly just when I am out walking and come by a good rock.

Ich fahre etwa 2,5 stunden bis zu meinen 200g Strand. 

Ich sammle sehr gezielt nordischen granit. Der ist fast unkaputtbar. Ich zerbreche nur wenige davon. Man findet ihn nach stürmen im Herbst häufiger als im Sommer