I did, and the mechanical rest was never good enough for an AR because the recoil was so light that there was no significant travel. It should work ok for .308 and larger. What I did in the end was gently hand-hold the AR and shoot 10 shots with and without a muzzle brake. I had an accelerometer on the rifle. All of the small brakes I tested were somewhere in the 30-40% recoil reduction range on an M4.

