Bought my soon to be 10 year old son a Remington 870 Express and I want to start him out with the lightest possible 20 guage #7 birdshot load that is available. He'll be starting with squirrel/rabbit hunting and I want to minimize recoil and we don't need speed to get the job done. Just good accuracy and judgement. Things that get hampered when a young shooter is flinching from expected recoil. So what is the lightest available? Please be specific. There are many varieties under just a brand name. I've noticed that not all of the companies put the same info on the boxes, so it can be a little hard to compare.