I had the same problem and the surface didn’t matter if I had an aggressive pre-load on the bipod. I replaced the feet with spikes and it solved the problem.
Kalinski Consulting in Yakima, WA. Caylen Wojcik has a solid background and is an avid hunter himself. He even has a Backcountry Hunters Course that he does over 5 days. I’ve taken several of his courses when he worked for another major manufacturer as director of training and one course since...