I'm fairly new to duck hunting, but I recently looked into those shells. They're pretty slow, only ~1300 fps @ the muzzle. If the ducks are close, then they're probably OK. Out over 35 yds, they aren't too good. I used the Remington Sportsman's with the same problem. Feathers would fly, but the duck went on. I switched to some faster shells (3.5" Rem's that my buddy had) and knocked them down on the first shot.

I'm going today to by a bulk pack of Winchester Super-X Dry-lok High-Vel. They are rated at 1500 fps w/ #2's or #4's and are costing $40 for 100 shells (4 25-shell boxes), plus a $7.50 rebate from Winchester. Bass Pro special.