I have a .50 disc elite and have shot both 777 and bh 209 through it. I may be in the minority, but I prefer the 777. I get excellent accuracy with it and for me the fowling on the bolt and in the breech area that I got with the bh 209 took a long time to clean up. Also the 777 is much more reasonably priced. This is just my opinion, take it for what it's worth.
Art