When I took up the subject of a magnum semi-automatic pistol a while back, I must have failed in my efforts to get one point firmly established. The only way to create an automatic pistol that provides the same kind of performance as the magnum revolvers is to build a bigger auto.This has been done with the Coonan, Desert Eagle, Wildey and Grizzly pistols. While all of these guns met with varying degrees of commercial success, they were all so big that they were difficult for most handgunners to carry and shoot comfortably. Readers have commented in such a way that I believe what they are asking for is a handgun the size of a conventional 1911 that delivers at least .357 Mag. performance. Some have asked for a .45 loaded up to higher levels of pressure and velocity performance. In my view, this is not a good idea.
There have been a couple of efforts to build such a gun, sometimes involving wildcatting. While some of these souped-up 1911s have met with limited success, they never seem to be durable. Even hot commercial rounds like the 10 mm Auto and 9x23 mm Winchester, which were commercially loaded by Colt and others, exist in pistols that don't have long service lives. If they are used at all, the full velocity loads in these guns should be used sparingly. And who wants to use a favorite gun “sparingly?”