Well, the SF does have a factory 458 Magazine box available (kinda tough to find though I am told), the CF does not. My 458 is built on a CF action and I ran it as a single shot until in my swaps I ended up with a Mag and follower out of a 300WM. My 458 will work as a repeater out of the 300 CF mag, but I load mine with 325gr FTX pointed ballistic tips and the Barnes TTSX ballistic tips. With those bullets it feeds fine, I have not loaded any of the 500-600gr RN or FP bullets to see if they will feed or not. I'd bet the RN will work but I am not going to hold my breath on the FP's.