so i've built a standard carbine 16 inch 300 bo ar that fte every single time using s&b, magtech, remington umc around120 grain. if i go lighter with barnes or hornady 110 it only does it every 9-10 rounds. i've got the gas block all the way open but still it won't eject anything heavier than 110. before i opened up the gb, it was having fte issues with the lighter grains too. but once i adjusted it, less ftes per mag. have yet to get it to run a full mag without any fte issues. standard weigh buffer, carbine tube, carbine gas, seekins adj gb. what else should i be looking for?