This diagram taken from Browning’s instruction book with the Auto 5 demonstrates the bronze friction piece plus the friction ring. (Image courtesy Browning). The Browning Auto 5 will nonetheless get the job done reliably without this adjustment, and seemingly will essentially operate with no bronze friction piece and friction ring https://www.safeheavenfirearms.com/product/barrett-model-82a1-50-bmg-tan-rifle-14031/