diff --git a/data/json/ammo_effects.json b/data/json/ammo_effects.json
index 6bc29a7ee0b92..d9e9017f9d062 100644
--- a/data/json/ammo_effects.json
+++ b/data/json/ammo_effects.json
@@ -8,7 +8,7 @@
       "intensity_max": 0,
       "radius": 0,
       "radius_z": 0,
-      "chance": 1,
+      "chance": 100,
       "size": 0,
       "check_passable": false,
       "check_sees": false,
@@ -89,7 +89,7 @@
   {
     "id": "PLASMA",
     "type": "ammo_effect",
-    "aoe": { "field_type": "fd_plasma", "intensity_min": 2, "intensity_max": 3, "chance": 2 }
+    "aoe": { "field_type": "fd_plasma", "intensity_min": 2, "intensity_max": 3, "chance": 50 }
   },
   {
     "id": "EXPLOSIVE_HUGE",
diff --git a/src/ammo_effect.cpp b/src/ammo_effect.cpp
index edc8a5a74d244..38142e95fcf50 100644
--- a/src/ammo_effect.cpp
+++ b/src/ammo_effect.cpp
@@ -100,8 +100,8 @@ void ammo_effect::check() const
     if( aoe_size < 0 ) {
         debugmsg( "Value of aoe_size cannot be negative" );
     }
-    if( aoe_chance < 0 ) {
-        debugmsg( "Field chance divisor cannot be negative" );
+    if( aoe_chance > 100 || aoe_chance <= 0 ) {
+        debugmsg( "Field chance of %s out of range (%d of min 1 max 100)", id.c_str(), aoe_chance );
     }
     if( aoe_radius_z < 0 || aoe_radius < 0 ) {
         debugmsg( "Radius values cannot be negative" );
diff --git a/src/ammo_effect.h b/src/ammo_effect.h
index 50b13d53a096a..e13cb6fe0f6fd 100644
--- a/src/ammo_effect.h
+++ b/src/ammo_effect.h
@@ -25,7 +25,7 @@ struct ammo_effect {
         int aoe_intensity_max = 0;
         int aoe_radius = 1;
         int aoe_radius_z = 0;
-        int aoe_chance = 1;
+        int aoe_chance = 100;
         int aoe_size = 0;
         explosion_data aoe_explosion_data;
         bool aoe_check_passable = false;
diff --git a/src/projectile.cpp b/src/projectile.cpp
index ba229a8862206..8bcbdb09532ce 100644
--- a/src/projectile.cpp
+++ b/src/projectile.cpp
@@ -95,7 +95,7 @@ void apply_ammo_effects( const tripoint &p, const std::set<std::string> &effects
     for( const ammo_effect &ae : ammo_effects::get_all() ) {
         if( effects.count( ae.id.str() ) > 0 ) {
             for( auto &pt : g->m.points_in_radius( p, ae.aoe_radius, ae.aoe_radius_z ) ) {
-                if( one_in( ae.aoe_chance ) ) {
+                if( x_in_y( ae.aoe_chance, 100 ) ) {
                     const bool check_sees = !ae.aoe_check_sees || g->m.sees( p, pt, ae.aoe_check_sees_radius );
                     const bool check_passable = !ae.aoe_check_passable || g->m.passable( pt );
                     if( check_sees && check_passable ) {