Pretty much.Gotta love the spin.
I would not touch one of those carbon 15 lowers.
Carbon is a great material when used for bending and tensile properties. But carbon composites suck for bearing strength and compression loads. They're no doubt light(er), but weight aside, I don't gain any benefit from from the rest of the piece.
I'd have to be swimming in acid to wreck the aluminum pieces on a standard AR.
edit: Though all manufacturers have to start somewhere. I know people did and do have similar feeling about Glock receivers. And it appears the cracking issues was largely a problem with earlier models. So, maybe they're okay. But they're not mainstream enough for me yet.