The 75 fps gain was with the 250 grain Swift A-frame loads. With my 300 grain loads, I only gained @ 55 fps. If I had it to do over again, I doubt I'd do the conversion. When my P.H.s have seen the Ackley round though, they get all excited. It really turned them on. Fortunately, I've shot well with it, so they all think the caliber kills like lightning.