Will the Real British .45 Revolver Cartridge Please Stand Up?

The title of my column is somewhat facetious because there are several British cartridges that qualify. My interest in them is twofold: I own a very shootable Webley & Son “WG” Target revolver marked “.450/.455” and an early Colt New Service. I also get questions about converting .455 revolvers to shoot more common ammo. There are more ballistic issues at play than meet the eye.

Britain’s series of .45-caliber centerfire service cartridges dates to 1868 with the .450 Adams revolver and cartridge. The Adams was issued until about 1880 but saw secondary service into World War I and remained popular for target shooting well into the 20th century. The stubby case was only 0.690 inch long.

The .450 cartridge was underpowered, and the revolvers were as slow to load and unload as a Colt SAA. The British military arsenal in Enfield attempted an improvement but effectively created a “horse designed by committee” instead. The 1879 Caliber .476 Enfield revolver had an innovative yet dodgy selective simultaneous ejection but loaded through a single-action style gate. Its awkward, primitive grip shape was carried over from older service revolvers.

The .476 cartridge case shared the head dimensions of the .450 Adams but was 0.870 inch long. Unexplainably, the .476 cartridge regressed to a heeled, outside-lubricated bullet about 0.475 inch in diameter, yet bores were much smaller. The revolvers were available and issued before new .476 ammo was finalized.

General displeasure with the Enfield forced the adoption of a vastly superior Webley & Son design in 1887. The “Pistol, Webley, Mk I” and its offspring served the Empire and its colonies for some 80 years.

The Mk I revolver fired the “new” .455 Mk I cartridge that was virtually identical to the .476 except for a proper, inside-lubricated, 265-grain, 0.455-inch lead bullet. The Mk I was also called the .455 Eley and, in North America, the .455 Colt.

The .455 Mk I was loaded with blackpowder; a smokeless-powder variant, the Mk II, replaced it about 1897. The Mk II case was shortened to 0.770 inch for better smokeless efficiency. Subsequent “marks” reflected a different bullet style, finishing with the Mk VI (1939) with a 265-grain FMJ bullet. The Mk II case length continued through the service life of the cartridge.

There is also a .455 Webley Auto cartridge for Webley & Scott and Colt semiautomatic pistols. However, the revolver cartridges cause the most confusion.

Obviously, ammo has always been the reason handgunners want to rechamber .455 revolvers to something available. The .476 Enfield and .455 Webley/Colt variants are, for all practical purposes, dead; the .450 Adams and the .455 Mk II are alive but on life support.

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Fiocchi still sells both .450 Revolver and .455 Mk II ammo loaded with lead bullets in its Heritage line. Pressures are 720 and 900 bar respectively; bar is the European CIP pressure unit. There is no direct correlation/conversion between CIP’s “bar” and SAAMI’s “psi” pressure protocols, but for comparison, CIP shows a max of 1,000 bar for the .44 SW Special.

Beyond case availability, handloading has issues. Starline makes .455 Mk II empty cases, and .45 Auto loading dies work okay except for crimping the short Mk II case. If you have a can of Bullseye powder, you’re set. The big issue is a proper bullet.

You need a soft, hollowbase (HB) lead bullet. Military revolvers may have chamber throat diameters smaller than barrel diameter, and Webley barrels have shallow rifling. A gunsmith I know found Mk VI revolvers with tight barrel throats as well. Jacketed bullets will not play well with those issues.

Only a soft HB bullet can safely handle that, and such bullets are simply not available from major component suppliers. You have to cast your own or buy cast bullets.

Lyman discontinued its two .455 HB molds (#457195 and #457196) years ago. RCBS had a special-order 455-265 HB mold for Webleys, but Midway says it has been discontinued. I found a maker in Slovenia, MP Molds (mp-molds.com), that offers an extensive selection of newly manufactured hollowpoint and hollowbase bullet molds, including three for .455 Webley. MP molds get high marks in cast-bullet forums I’ve surfed.

That’s a lot to take in and shows why I get conversion questions. As much as I abhor such alterations, I will discuss them in the interest of safety.

The Webley rim is much thinner than most U.S. revolver cartridges, and space must be provided when converting. The metal comes off the back of the cylinder, never the standing breech. I prefer recessing rims to shaving a lot of metal off the back of the cylinder.

The lead-bullet issue limits choice of conversion cartridges for the non-handloader. Smith & Wesson and Colt double-action .455 revolvers have cylinders long enough to rechamber to .45 Colt, and their chamber and bore dimensions are usually proper. The .45 Colt is factory-loaded with hollowbase lead bullets.

The more common Webley Mk VI is a different story. Its cylinder is short because, unlike the S&Ws and Colts, it needed only to chamber the short .455 Mk I and later cartridges. The best-of-all-worlds solution here—the .45 Auto Rim cartridge—sadly has been discontinued. Its length and diameters worked, and it was loaded with an HB soft lead bullet. All you needed to create was a deep rim recess.

Only consider .45 Auto if a gunsmith verifies chamber throats are no smaller than 0.453 to 0.454 inch or, if required, reams them to that size. Have the diameter of the barrel throat verified as well. Don’t expect accuracy with 0.451-inch jacketed bullets going down a bore with shallow rifling that is usually 0.455 inch.

How capable is an unaltered .455 revolver with proper factory ammo? The only one I’ve wrung out at distance is my Webley Target, likely made before 1897. With old CIL/Imperial .455 Colt ammo, it groups under six inches at 100 yards on a steel plate and is impressive out to 180 yards.