I don’t suppose it’s any secret that I have a ‘thing’ for percussion revolvers converted to fire cartridges. I also have a thing for Big-bore snub-nosed revolvers. Then I found out the Kirst makes drop-in conversions for a number of reproduction percussion revolvers. I was pretty happy to discover this for obvious reasons.

This brings us to the Colt Walker- the first commercially successful Colt revolver. This was a massive Horse-pistol built with the mission to be able to drop a horse with a single shot.

Reproduction Walker Colt

Originally designed to fire a conical Pickett Bullet on top of a charge of 60 grains of black powder. These bullets were fussy; they had very little bearing surface and if carelessly loaded they could tilt in the bore and accuracy when this happened was terrible. People took to loading them with ball or more conventional bullets. With the long barrel and heavy powder charge these were arguably the most powerful handgun available until the introduction of the .357 Magnum.

Obviously this would be a ludicrous candidate to be turned into a snubby, but a shorter, handier version might be neat… especially with a Kirst conversion to .45 Colt.

.45 Walker reproduction with a Kirst gated cartridge conversion.

But this is such a large gun that the cylinder is quite long for .45 Colt. Considering that significantly smaller and handier guns can be converted to this cartridge it seemed silly to convert a Walker to fire it.

The .45 Colt fired a conical bullet on top of a charge of 40 grains of Black powder… but the Walker fired a bullet on top of 60 grains of Black Powder… 50% more powerful. But given how long the cylinder is what if one bored the cylinder out for a longer cartridge- a .45-60 as it were?

Concept of a ‘long cylinder’ cartridge conversion with a 5-1/2″barrel

The Walker revolver could take a 60-grain charge of black powder and it’s cylinder was iron. Modern reproductions are made of steel and are significantly tougher. It ought to work…

It does, and someone beat me to it. It’s called the .45 BPM (Black Powder Magnum.)

Colt Walker conversion with .45 BPM and .45 Colt for comparison

With various loads this cartridge develops 500-600 ft.lbs. of energy at the muzzle. It’s is loaded into .460 S&W Magnum brass. The Kirst cylinder has to be reamed out for the extra length and the rim recesses have to be enlarged to accommodate the larger-diameter rims of the .460.  I immediately cringed at the thought of some idiot sticking a .460 Magnum shell in the gun… which would explode when fired. But factory .460 ammunition would actually stick out of the front of the cylinder and prevent the gun from functioning.

My dream of a Walker Cartridge Conversion in a worthy cartridge seemed much more realistic. But not without issues… this cartridge was designed to be fired from a 9″ barrel, and with some loads there isn’t much point in going beyond 50-52 Grains of black powder. There’s a point of diminishing returns where adding more powder just means more smoke and fire, and that point would be at an even lower threshold with a 5 to 5-1/2″ barrel. Essentially the power of the .45 BPM would be wasted in the shorter gun.

OK, but there should till be room for improvement over .45 Colt. Suppose one shortened the .460 brass to a length between .460 and .454 Casull? Turned down the rim to the same diameter as .45 Colt instead on enlarging the rim recesses? .460 would not longer chamber at all. Stoke this with 50 grains of black powder behind a 250 grain bullet with proper compression of the powder and while it wouldn’t be as powerful as the .45 BPM it would see significant gains over .45 Colt. This could also be loaded with Red Dot smokeless powder (in a much, much smaller quantity) as this powder mimics the chamber and down-bore pressure curves of Black Powder. Certainly the local indoor ranges would be happier with me if I did this…

So all I have to do is buy the gun, buy the Kirst converter, modify it and invent a new cartridge. Uh, sure. Of course I could just go buy a .45 Colt Ruger Super Blackhawk and load it up to loads just as powerful. But that wouldn’t be nearly as cool, would it?

No. No it would not. Stay tuned- this could happen…

Tinker Pearce, 03 April 2017

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