The older Longbeard XR was pretty darn solid stuff and killed a lot of turkeys. But in multiple recent experiences for me, it does not shoot well at all and is not a 40 yard gun. If you are not convinced, you can also go to Blue Collar Outdoors on you tube and watch their tests in the last two weeks which also show the same thing. With three different premium chokes, they got one pellet on the brain and spine at forty yards out of three different tests. Two of the three tests had none in the kill zone at forty. Not good.
But As far as good chokes for the 500, I have had great results with the Trulock .575 and .585 (Precision Hunter) and the Indian Creek Black Diamond .570. The Patternmaster Ananconda Striker .570 (Gas over constriction) will just about match them step for step as well.
P.S. - Please let us know if you get different (better) results with the newer Longbeard XR. A different choke that others may have missed might find the sweet spot and bring it all back together and I am always learning something new. Good luck with your gun.