ive been asked to help build an AR10. Currently looking for the barrel, gas block and BCG. I'm thinking 20" with a 1/10 twist. I have up to $600 for this. BCG? A high pressure modle with a pin that's not tricky to find. I've got about $275 for this. I'm going to let him try my one and two stage triggers. He wants to hunt with it and that lends me to think a two stage. He's allocated me $250 for the trigger. Ideas! Know who's got sales going on?