I'm new to the shotgun world... I picked up a Remington 870 Express from Dick's Sporting Goods a few days ago, but just got to shoot it (completely stock) for the first time today. Now my shoulder is red and sore as hell lol... Is this supposed to happen? I've had to have watched like dozens of YouTube vids with teens, women, or men young and old, and they seemed to let of shot after shot without a problem... I took off the butstock that it came with, and put on a Hogue Pistil Grip and forend. Should this be easier to shoot?