There's several ways to do this but the following is what I recommend:
1. Start the Bosmos camp mission.
2. Rearm properly for the mission at the armory but grab a pistol\handgun.
3. Grab a magazine for said pistol\handgun.
4. Fire some rounds of said pistol\handgun until the magazine is around 25% or less.
5. Meet with James and start the mission briefing.
6. Accept the Supply Network mission.
7. Notice how Kerry reports he is low on ammo while the initial video is playing.