You shouldn't lose any sleep over it being cast. I have a older DPMS cast lower with at the very least 15,000 rounds through it and it's going fine.
Don't buy into the internet commandos that poo-poo DPMS. I have used their stuff for years with ZERO problems.
In my safe right now is 3 lowers, 3 bolt carrier groups and a half of dozen LPK's, in addition to hundreds of small parts in my parts bin. I have no reason not to continue to use their stuff.
You want problems, ask me about my Bushmaster.