Love mine but I'd suggest staying away from the cheap steel case ammo. Tends to wear down the lower locking lug on AR's as it's striping the top round out of the mag. I'd be interested to know your thoughts on the Carbon lower. Mine's traditional aluminum and I've heard mixed results, good and bad, about the durability of Carbon guns.
Oh, and you have a bunch of that cheap steel cased .223, your Ruger should chew threw them just fine.