diff --git a/src/PrimaryGeneratorAction.cc b/src/PrimaryGeneratorAction.cc
index b6cde79..01d876b 100644
--- a/src/PrimaryGeneratorAction.cc
+++ b/src/PrimaryGeneratorAction.cc
@@ -121,10 +121,18 @@ void PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
     G4Exception("PrimaryGeneratorAction::GeneratePrimaries()",
       "MyCode0002", JustWarning, msg);
   }
-
-  // Set gun position
-  fParticleGun
-    ->SetParticlePosition(G4ThreeVector(0., 0., -worldZHalfLength));
+  //draw particle position from a unit distribution in x-y with +-5 cm around the center
+  G4double x = -1000;
+  G4double y = -1000;
+  G4double x_width = 15;
+  G4double y_width = 15;
+  while(x < -x_width/2. || x > x_width/2. || y < -y_width/2. || y > y_width/2.){
+      x = G4INCL::Random::shoot()*x_width - x_width/2;
+      y = G4INCL::Random::shoot()*y_width - y_width/2;
+  }
+  fParticleGun->SetParticlePosition(G4ThreeVector(x*cm, y*cm, -worldZHalfLength));
+  //printout for checking
+  G4cout << "shooting at " << x << " " << y << " " << -worldZHalfLength << G4endl;
 
   fParticleGun->GeneratePrimaryVertex(anEvent);