I own a Walker Colt made by Uberti of Italy that’s now part of the Beretta Corporation.
I have studied black powder guns for decades including the history of the Walker.
Loaded with it maximum charge of 60 grains of FFFg black powder behind a .454 round ball, a conical or the original picket bullet it can reach the level of the .357 magnum but will not surpass the .357 magnum. If you load it with a max charge of hodgens Triple 7 FFFg black powder substitute you can equal the .357 mag but that will create too much wear on the gun especially the barrel wedge that’s designed to take the beating instead of the frame.
It should be noted that one guy loaded his walker with 60 grains of Triple 7 and it blew the barrel off the gun. This is because Triple 7 is 15% more powerful than black powder.
So no it can’t equal the standard .44 magnum and could never surpass it.
It is a fine revolver; huge, powerful and beautiful.
When Mr. Walker of the Texas Rangers asked Mr. Colt to make him a horse pistol, Mr. Colt came through. This was a pistol fully capable of killing a horse. But it was not designed to be worn on the hip like Josie Wales. Instead two walkers were hung in a special holster hung on the saddle horn. And I can assure you this monster is heavy! And I can hit a paper plate at 100 yards every time with mine.
The back sight in a notch on the hammer that when pulled back gives you your sight plane. And its set up to shoot high at close range which takes some getting used to but is great for long shots.
I have come up with special loads for the walker and have two of them now. They are hung over the gas tank of my ATV, my iron horse lol.
So there you go. And I could provide you with links to back up everything I wrote. Some regulars here know I’m up on this gun.
The Walker Colt was the most powerful revolver on earth until the .357 magnum came out in the 1930s. So it has a real foot hold in the history of firearms.
http://www.hackman-adams.com/guns/ColtWalker.htm
Oh it was the History channel that came up with it being equal to the 44 magnum
http://www.thehighroad.org/archive/index.php/t-36521.html
Never believe the History channel they are full of idiots.
More on the walker
http://thetruthaboutguns.com/2010/11/roy-hill/gun-review-uberti-colt-walker-reproduction/