We used to use a steel outer shell and poured lead jaws custom to what we were unscrewing. The barrel was grabbed in lead also with rosin and tightened down with a two ton jack in a steel box. The wrench was two bolts with a handle and a set of square outer jaws. I just eliminated the middle man and used straight aluminum so it could deform if need be and was cheaper to make. Usually there's been something to grab, a shape. The long handles help to avoid jerking the receiver. I'd reassemble the way Chuck suggests...dry will be good.