Interesting, but I think that's a flawed argument Bergmen.
A FA is a finely tuned high end revolver. with incredible tolerances. (I've been drooling over them for years) I think the reason they don't want you shooting .45 Colt, is that they don't want you scarring up all their hard work for being a cheapskate on the brass with a $2000 or so pistol.
I don't like shooting .38's in a .357 either, and the solution is the same for both... Use the longer case and download the pressure.
Standard 454's of every other brand can chamber both .45 Colt and Casull, .460's chamber all 3. I've not heard of a .454 that absolutely
cannot use .45.
"Cannot" is not the same as "for the love of Mike, PLEASE just buy another Cylinder"
http://www.chuckhawks.com/460_SW_Mag.htm
The new cartridge is a lengthened version of the .454 Casull, itself a lengthened version of the .45 Long Colt. So both of those cartridges can be fired in a revolver chambered for the .460 Magnum.
http://www.reloadammo.com/454casull.htm
The .454 came out in the late 50's and was the big, bad boy in town, till the advent of the .500 S&W mag and now, the .460S&W magnum. This caliber, designed by Dick Casull, is great for us who have lots of .45 Colt ammo (I reload for cowboy shooting, but want a gun that can handle everything up to this magnum with very heavy lead bullets moving out at speeds in the 1300-2000 fps range.)
http://en.wikipedia.org/wiki/.45_Colt (actually only checked this as an afterthought)
The .45 Colt became the basis for the much more powerful .454 Casull cartridge, with the .454 Casull having a slightly longer and stronger case. Any .454 Casull revolver will chamber and fire .45 Colt, but not the inverse due to the Casull's longer case. The .460 S&W Magnum is a longer version of the .454 Casull and the .45 Colt. Likewise, .460 Magnum revolvers can chamber and fire the two lesser cartridges, but again, not the reverse
But I agree with you otherwise, use the proper length brass for the proper caliber gun, except where unavoidable.