I would like to change a 64 to 357. It is a 2" and would be a truck, boat,barn etc gun. will a 158 gr Lead SWC HP loaded to + p + work?? sure but it is more to make a "new" gun. I have 2 3/4",3", 4", 6" 357 mags. Do I NEED it- no would I like it yes. Thank You.