I did buy the A.A. .50 Beowulf upper and mounted it on a S&W M&P 15. It dropped right in and works perfectly. I was wondering whether I should have a heavier buffer and buffer spring, but A.A. said it's not necessary. I was going to mount a nice Leupold scope on it, but I've just lost about 10,000 dollars in the stock market because of the Coronavirus scare, and I'll have to wait until better times to spend money on "unnecessary" things. So I mounted on it an old Bushnell that I had on another rifle before I replaced with a Leupold a year ago, and I'll have to make do with that.
Folks, this epidemic (or pandemic) is serious business--take it seriously. I would have liked to go to the NRA general meeting but I doubt it will be held this year, what with the tornadoes that hit Nashville and the danger of contracting the disease in places crowded by people from all states--even those severely hit by this deadly disease.
Good luck to all. Avoid crowds, public transportation, medical buildings, theaters, stadiums, parties, political rallies. Shop for groceries at night, when there are few people in the stores, remember that a sneeze or cough will propel the virus up to 15 feet or more, and that it will remain airborne for up to 30 minutes. And wash your hands often and don't touch your face before washing your hands. Carry some sort of disinfectant in a bottle and rub it onto your hands often
Sorry about the O.T., but these are hard times.