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.
50 BMG 1rnd AP.dat
GUID 10e9e70455ae4c6a81d7bf15396a6780
Type Magazine
Rarity Rare
ID 59577
Size_X 1
Size_Y 1
Size_Z 0.25
Amount 1
Count_Min 1
Count_Max 1
Calibers 1
Caliber_0 56210
Spread 2
Shake 1.25
Recoil_X 1.5
Recoil_Y 1.5
Ballistic_Damage_Multiplier 2
Tracer 48
Explosion 55073
Explosive
Delete_Empty