I over heard some guys at my local gun shop talking about 50 bmg upper for an ar-15. They were saying the price was in the $1200-$1400 range. I didnt get a brand and didnt get to talk to anybody because they were busy and I had limited time. Anyone have any info on this? How does it shoot? Any brands to stay away from? Is it just the upper or do you get a different stock too? Thanks.