To add to what 44man said, I have two experiences with Magna Port, one with an SW 625 in 45 colt and another with an FA 454.
The SW 45 shoots splendidly...it's a true one holer. I'm sure the porting helps with the accuracy and it definitely helped with recoil.
The FA 454 is a MagnaPort Stalker with a 10" bbl. The thing is absolutely gorgeous. It also came with a .45acp cylinder, TSOB base and rings, and a Bausch & Lomb 2-6. The jeweling and polish work on this is tastefully done and just superb. Gate, hammer, trigger are polished (except that the trigger and hammer are jeweled one side, polished the other), cylinder rings polished, two bands on the barrel and on the grip frame just below the the trigger. Inverted target crown and quad porting.
The action work (done by MagnaPort) is excellent. Best part...bought used, hardly fired in 454 and unfired .45 acp cylinder for $1395 Shoots keyholes at 50 yards.