I use a standard Harris AR bipod adapter (#5 maybe?) on my M500As. You'll have to remove the heatshields temporarily to install it, but aside from that installation is a snap
Most of my rifles (even carbines) get a bipod stud for sighting-in purposes. I don't trust myself enough to zero a weapon offhand.
Here's a Harris bipod stud on one of my M500A equipped carbines:
I had to add the washer to give the stud enough "meat" to hold onto. It has been anodized black since this pic was taken