I dont have one...I know a man who does tho...problem is its a bit overkill really...mind you could be fun!
My .308 Is an Accuracy International AW...its a very precise tool...the Barret is a very powerful bit of kit but not quite as accurate....AI do a .50 now as well!!!
I shot a .50 Barret at a local army range...good fun, shooting steel plates at nearley 2 miles!!!