Re: magnaporting.
Had them both. Mag-Na-Porting reduces recoil about 20 percent, but since the gases are directed up, the apparent reduction is more since you don't see the scope attacking your eye and causing a flinch. I did a .300 Weatherby years ago and it made a completely different rifle out of it. A brake with an expansion chamber can reduce the recoil up to 65 percent. It seems to me to be louder than the MagNaPorting however. I'd avoid MagNaPorting a high pressure pistol round such as the .454 Casull if you plan using hard cast bullets. The ports blow off the lube and the last inch leads like crazy. I know.