Yes! Got the hard badge!!
Heres what I did it it helps...
Picked "welcome to hell" level, turned off all other things except zombies and devils, and did nightmare mode.
Then, before the zombies came, placed all my turret guns and mortars.
When you get an upgrade of either of those turrets, you will get full ammo.
While your guns are killing all the zombies, keep placing the turrets as you get them.
Once the level is done, use your minigun to blow away zombies so they drop more ammo for your turrets, but don't go too close to the edge of the map. Then, when you get turret gun or mortar ammo, palce them all near your barricades, outside of the barricades if you have to.
Keep this up and once you get to level 50, a TON of devils will appear. In that level just keep running and with luck you will not get hit.
Hope this helps
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