Ryan moves forward to lend the rebels an extra gun. Three moving targets are certain to cause more confusion and be harder to hit than two, not to mention that Ryan can afford to be a little more brazen in drawing fire.

Holtzmann shield generators are fun like that.

If there's a pause in combat, he'll pick up a few grenades and one of the submachine guns. Yes, he's got his rifle but limited ammo. Better to have something where his odds of getting more munitions are good.