I have been trained in the use of and when not to use the babbit bar. It is not used to correct the clocking of a revolver barrel. It is used in the conjunction of the correct gauges to realign a bent frame. It can be used to correct the correlation of POA and POI, usually in fixed sight revolvers. I have used it to correct a frame badly warped by the 'bubba hammer handle' method of removing a barrel from said frame. I have used it to correct a top strap bent down to touching the cylinder. I have used it to bring the POI closer to POA. There are other more minor uses around the pistolsmith work bench. It does take some muscle memory for gauging the amount of force to be used in any given instance.

FYI, merely wacking a frame back into alignment is not the final solution. Bend steel and then bend it back and one dimension or another will 'grow'. That is going to have to be taken into account with head space, barrel/cylinder gap and timing. Pre model numbered frames will be of slightly 'softer' steel and will bend easier. Care must be taken when moving from a later frame and getting use to the harder blows necessary to achieve desired results to an older softer frame requiring the same corrections. It takes a much softer blow to move an older frame the equivalent distance as compared to a newer frame.

Many years ago, custom quality shotgun makers 'regulated' the barrels of a side by side or an overunder by wacking the barrel in the appropriate spot with a lead babbit hammer. There were specialists in those custom houses that did only that job.