Unlock The Railgun (GTA Online and GTA 5 Story Mode) - GTA BOOM
I managed to complete the bunker shooting range challenges to be able to hold 5 more of every throwable item in game however it was a pain in the ass to get
Gunrunning - GTA 5 Wiki Guide - IGN
Bunker Shooting Range Challenges Discussion - GTA Online - GTAForums
List of all Bunker Shooting Range challenges in GTA Online
New gold guns? - GTA Online - GTAForums
List of all Bunker Shooting Range challenges in GTA Online
Gunrunning shooting range is just stressful... - GTA Online - GTAForums