This item is not included in any spawn asset, but it doesn't necessarily mean that it doesn't spawn naturally on any of the maps.
CA_40_Buckshot_3.dat
GUID 4a32d13dd6e24910b250bcc1014cdbbf
Type Magazine
Rarity Legendary
ID 6216
Size_X 2
Size_Y 2
Amount 3
Calibers 1
Caliber_0 4177
Tracer 4055
Delete_Empty
Pellets 8
Damage 0.5
Muzzle 4
Blueprints 1
Blueprint_0_Type Ammo
Blueprint_0_Supplies 1
Blueprint_0_Supply_0_ID 6216
Blueprint_0_Build 4180