Sniper rifle made that level a breeze. You can just sit back and pick off everyone before they get close enough to charge you.
That's what I had been using, but even when trying to be careful about ammo, I still got to what I assume (or hope) is the last section of the level with only 3 bullets left. Other than the 1 crate that gives you a bountiful 4 bullets, is there some other way to get more ammo that I'm missing?
There's an ammo crate on each level after the first (or at least I couldn't find a crate on the first level). You can camp out at each one and refill whenever you run out of ammo.
I have no idea why you can only get more ammo once you're completely empty.
Wait, so if you get more ammo and then use up THOSE bullets, you can go back and get more? I had assumed it was a one time thing! That should definitely help (even if it only gives you 4 bullets at a time)