My Kreighoff O/U .458 double rifle has 20 gauge 3" Magnum shot barrels, choked modified and full. I used them to good effect on ducks and sand grouse in Kenya. Of course the balance is different, but shooting with them at clays certainly improved my comfort level and familiarity with the double triggers. All my other O/U's (Perazzi, Beretta, Browning) have single triggers.