Ok, now that I've calmed down, I can accept the fact that it's a good AA rifle, and he probably thought it's all he would need since he prepared it before they were ambushed. I can also accept that I don't know how long it takes him to switch guns. What I can't accept is the possibility (it's not confirmed) that he was using it to save ammo. When people are dying, you worry about things like cost and collateral damage later. And an LMG (possibly with tripod mount) and tracer rounds would also be good at AA.