The smooth way to attach a Valhalla bipod to a rifle with a synthetic or wooden stock, or to a rifle with a pre-made spigot hole like the GRS.  Carefully line up the bipod on the front of the stock, measure the placement of the spigot 12 times, ensuring a placement that allows the bipod to slide on without interfering with the barrel, and drill a hole parallell to the bore and insert the adapter with some glue. Or oil it lightly and press into a pre-made spigot hole. Secure with an M5 bolt.