just finished my first ar build i used a rra lower and a model 1 upper in 6.8 . anyway, i'm excited doing more of these. what i'd like to do next is an m4. but i'd like to do it with my custom logo and custom serial numer on the lower. i've talked to olyarms and they said that they would do it for me. but i'd like to know if there's any other company's that would do that for me.