Sigh...this was not an uncommon practice when it came to old ordenance. I have seen cannon balls also converted into gate weights and even one for a clock weight. I had a four pounder with a link welded to it that I thought might be half of a chain-shot, but the weld was definitely more modern. Makes me mad when artifacts are treated this way-
That being said, yours at least hasn't been blow-torched, cut in half or fiddled with too badly. The binding iron straps don't take away from the piece,in my opinion.