Isn't it just steel cased ammo though? The cheapest prices I found was about $130 per 1080. It's cheap enough but it's still just blasting ammo. I've got an AK-47 that serves as a blaster already. I looked a S&W 5.45 upper but I decided I would never shoot enough to justify the purchase.
Terry
SoG has non corrosive packs of 1080 for around $109. Or at least they did a while back.
You can buy 10,800 rounds and an then an upper if you already have a lower and still come out ahead if you never see another round for sale if you just want to go bang.