Generally not a good idea as barrel can be damaged by out-of-true BBs. However on a low-power gun where they have been shot into a soft backing like old shirts or similar, then maybe they will be OK.
BBs are nasty richochetting things and I suggest using lead pellets or lead shot instead, neither of which can be reused.
You can recycle your steel BBs though, collecting them with a magnet and putting them in the scrap steel bin.
BBs are very cheap! why should you reuse?
What pistol have you? If it is an airsoft which fires plastic 6mm ball shot then I think it is still good practice to use new ones.