will it damage the gun if they break
yes but not if you shoot them into something hard. They get a flat spot and they will fly erratic. we used to take them out of the bb trap and re-use them and wonder where the accuracy went.
i sometimes reuse mine. I just spend half and hour pickin up bbs in the backyard, washing it, and inspecting for any damages on the bb.
Make sure they are still round and not damaged. If they are damaged or have debris on them, you will scratch the internals of the air gun, and they will not shoot straight. An idea is to have a sort of BB catcher. Have a sheet or blanket hanging up somewhere, and make it so when you shoot at it, the BB's roll down the sheet and go to some kind of container like a bucket or box. Then just get the BB's out of the container, clean them, and shoot them again.
