I don't shoot a mossberg 500, but I shoot .665 with #5 shot. .660 should be a good choke for #6's especially with Longbeards, The 500 mossberg might like a little more open choke. haven't heard of many people getting bad patterns with longbeards. Maybe some mossberg hunters will chime in. I don't count holes but I have read here that the minimum number of shot is 100 shot in a 10 inch circle at the maximum range you want to shoot. I have read a couple of posts that people said the Jellyhead choke did not do well with their guns. Good Luck