I just bought a Noveske 18"upper complete with staked bolt but no bolt carrier, and a stripped Noveske lower. I want to build this rifle top notch so what bolt carrier should I buy for it? Also what trigger is better....geissele, timney or is there something better than those two? Also I bought a Noveske end plate and it says it needs to be staked by an armor or gunsmith. Why does this need staked?