Forgive an ignorant fool for asking a question that's quite possibly silly. Kinda new to the forum and I'm hoping to start my very first build. I've put in an order for 3 stripped lowers just in case Obamination wins and I might as well learn something. Ordered two 5.56 and one 6.8 spc lower. Do LPK's for 5.56 lowers interchange with 6.8 lpk's? I know the mags don't but I wasn't sure about the other parts.