The .45 Colt cartridge is a wonderful relic of days gone by. Conceived in the immediate post-Civil War era, the old slugger first sent that half-ounce slug lumbering downrange some 144 years past. It served the nation well in the Indian Wars and in the difficulties in the Philippines. Unofficially, it has served police officers from the New York State Troopers to Santa Ana PD. The salient feature of the round was always brute power, a quaint old belief that someone who deserves to be shot deserves to be proper shot. The .45 Colt bullet was massive, the velocity moderate, the effect monumental. Nearly a century and a half later, the .45 Colt—with proper ammo—is as good as you can get when it comes to a combat cartridge. And yes, I am aware that it is exclusively a revolver cartridge. 
This was the cartridge that was most commonly loaded at home in recent years. It needed to be, because the available .45 Colt guns had not kept pace with the improvements in ammo. The last DA/SA Colt revolver was the much-lamented Colt New Service, which went out of print in 1942. Smith & Wesson delighted the big bullet boys by introducing the Model 25-5 in the late 1970s. That big N-frame got a fair amount of attention, but not enough to sell in the numbers that keep guns in their builder’s catalogs. So the .45 Colt cartridge hung on for use in the venerable Peacemaker and its clones. These guns simply will not prosper on a regular diet of high-pressure, hig- velocity, heavy-bullet ammo. In reality, the big S&Ws don’t do very much better. The makers of modern commercial ammunition are aware of these limitations, so they will never load high-performance ammunition in .45 Colt. Understandably, the big makers are afraid of serious liability issues when they make high pressure ammo that fits a gun which is identified as being that caliber.
Does this mean that the .45 Colt is commercially dead? Absolutely not! There are large numbers of very strong revolvers that will handle high performance .45 Colt handloads. They are, in effect, .45 Magnums. This fact has long been accepted among the handloading fraternity and the loading manuals often list special loads just for these guns. For decades, the strong Ruger Blackhawks have been loaded to the firewall and stay accurate. The big revolvers from Freedom Arms are even stronger. If you really need super performance in a portable handgun, you might want to consider one of the big Freedoms in .454 Casull.
This situation suggests that the .45 Colt is “two-faced” in the sense that it has two useful natures. One is ammo with traditional performance—big bullet, low-velocity—or anything that says “.45 Colt” on the barrel. The other is ammo put up in brass marked .45 Colt, for use in selected guns of known strength by advanced handloaders who are experienced and extremely cautious.