My rifle is deffinately a factory 300winmag.I think they were chambered in 300winmag,375h&hmag and 458winmag.Its a 1987 model.If the cost of rebarreling is goin to be close to what i paid for it,I think I will keep it a 300winmag.Does the CZ 550 come out chambered in 416 rigby?I had a look at a site today but I couldnt find a 416rigby chambered rifle.