Mark,
The former local gunsmith (and a friend), who spend many years at the Army Advanced Marksmanship Unit,building rifles for world class shooters, then spent many more years in his own shop cautioned me against this.He had experience with "spotting" when he tried it. I don't know if this was in one of the several Army shops he worled in, or his own shop. I also don't know whether the tanks were made of 200, 300, or 400 series stainless steel. I considered his advice as authoritative and accepted is experience as true.
Mike