I think you will find that the 458 suffers very little from a shorter barrel. In my experiance the bigger and slower you start the less effected the velocity loss is by shortening the barrel.
Sort of like old men eh?
I think a 22 inch barrel is perfect for a bolt in 458.
-------------------- Lovu Zdar
Mick
A Man of Pleasure, Enterprise, Wit and Spirit Rare Books, Big Game Hunting, English Rifles, Fishing, Explosives, Chauvinism, Insensitivity, Public Drunkenness and Sloth, Champion of Lost and Unpopular Causes.