Bore Diameter, Obsolete Cartridges, Etc

The 1860 Colt Army was a cap-and-ball revolver used during the Civil War.  Colt produced some 200,000 of them.  It was called a .44 caliber, but used a ball of 0.454 diameter.  (Nomially, a .45 cal ball), or a conical of the same diameter.

In 1866, William Mason went to work for Colt at the Hartford plant.  He patented a conversion to the 1860 Army that used a bored-through cylinder that would accept the newfangled brass cartridges coming into fashion.  The first of these revolvers used a straight-through boring of the cylinder that employed a cartridge with a heeled bullet.  The inside of the cartridge case was 0.430 in diameter and the forward part of the bullet was .45 cal to properly fit the bullet to the bore/groove diameters of the 1860 Army.  These new-fangled cartridges were called the .44 Colt.    This conversion revolver is now known as the Richards-Mason conversion.

Mason worked on a new pistol, the Open Top, but the Army rejected it, requesting a stronger frame and more powerful cartridge.   Mason re-designed the revolver with a top strap (like the Remington) and the first prototype was chambered in .44 Henry.    But, about that time, the Union Metallic Cartridge Company, in partnership with Colt, came out with a new, internally lubricated bullet and called it the .45 Colt.  Colt submitted this new revolver to the Army and they accepted it, along with the newer cartridge, in 1872.

Cartridges that use heeled bullets still exist, of course.  The most popular is probably the most sold cartridge in the world, the ubiquitous .22 Long Rifle.  But, I find it interesting that the .44 caliber 1860 Army and the 1873 Single action Army share the same bore diameter, regardless of what the cartridge might have been called. 

Nowadays, our popular .44 caliber revolver cartridges use a 0.429 diameter bullet.  This smaller bullet fits inside the 0.430 diameter cartridge case that we use for the 44 Special and .44 magnum.