During the fire fight with the robbers Rosewood gives Capt. Slade a M4 rifle. Capt. Slade removes the magazine to check the ammo then runs over and engages the robbers. Several times during this scene you can clearly see the magazine used in the gun is a metal magazine. Capt. Slade does a Magazine change when the camera changes angle the discarded magazine shown is a plastic Magazine (PMAG). Next the camera switches and Capt. Slade inserts another Metal magazine into his gun.