The Colt Peacemaker barrel length conundrum
When is a 7-1/2 inch barrel not a 7-1/2 inch barrel?
By Dennis Adler
This is a story about barrel lengths, overall lengths, conceptions, misconceptions, and interpretations, it’s also a story about how one gun can have two barrel lengths at the same time!
Let’s begin at the beginning, when Samuel Colt patented the revolver in 1835 (his first patent filed in Great Britain in October of that year) and again in February 1836 for his U.S. patent. (Colt knew that if a patent were filed first in the United States the same could not be applied for in Great Britain or France, whereas a U.S. patent could be granted regardless of whether there were foreign patents preceding it. He was pretty savvy for a young man).
Colt measured his barrel lengths by, well, simply measuring the barrel from one end to the other. His first handguns were open top designs, thus the barrel length was pretty clear. The back of the barrel was nearly flush with the front of the cylinder. A wedge passing through a slot in the barrel lug corresponded with a slot in the cylinder arbor, with the wedge passing all the way through to the other side of the lug and securing the barrel to the frame.
In 1847 Colt introduced the .44 caliber Walker pistol, and with it a change to the back of the barrel lug which was no longer flush to the face of the cylinder, but rather cleared the cylinder by an average of 3/16th of an inch. A forcing cone was added at the back of the barrel to close the gap between the barrel breech and the top cylinder chamber. This has remained the standard barrel to cylinder design to the present day.
When the Colt’s revolver patent expired in 1857, E. Remington & Sons became the first major American armsmaker to introduce a competitive large caliber pistol. The design of their 1858 Remington-Beals Navy and Army models eschewed the prevailing Colt design by using a solid topstrap frame with the barrel threaded into the front of the frame. This was a stronger design than the Colt. And this is where the first confusion began.
Folks started thinking that the barrel was measured from the front of the frame, but the threaded end of the barrel’s bore continued through the frame, and ended directly in line with the top cylinder chamber, where the forcing cone came up almost against the front of cylinder. The forcing cone was necessary to provide as close to a solid seal between the back of the barrel and cylinder chamber as possible in order to prevent gases generated by the ignition of the gunpowder in the chamber or cartridge from escaping; simple enough again, unless you mistakenly begin measuring the barrel from the front of the frame, and not the front of the cylinder or the back of the forcing cone. And you would be amazed how many people have made that mistake over the last 158 years since the first Remington revolver was built! It is still a problem, and it has happened as recently as this month with the confusion over the new Umarex Colt 7-1/2 inch barrel CO2 model. On the box it states “BARREL LENGTH: 6.75 inches.” Did Umarex and Colt get it wrong? Depends upon what you are measuring, and how.
Let’s jump back to 1873 when the Colt’s Patent Fire-Arms Manufacturing Co. officially introduced the Peacemaker. It was patented in September 1871 by William Mason, Colt’s Superintendent of the Armory and the first examples were built late in 1872. The first Colt Single Action Army revolvers had 7-1/2 inch barrels just like the latest .177 (4.5mm) caliber Umarex Colt Peacemaker pellet models. So where does the confusion about a 6.75 inch barrel length come from?
It’s a little ironic that the method used for measuring the barrel length of the new 7-1/2 inch pellet model Peacemaker is unintentionally taken from the front of the frame to the muzzle, which is 6.75 inches. But that is not the reason the gun is listed as having a 6.75 inch barrel. In order to have an accurate copy of the original .45 Colt SAA model, the barrel has to be 7-1/2 inches measured from the muzzle to the front of the cylinder, and the Umarex Colt is within 1/16th of an inch because the forcing cone for the airgun is a little shorter than a cartridge gun’s. But, and here it comes, the .177 caliber rifled barrel for the revolver is recessed inside the .45 Colt barrel by 11/16ths of inch. This totally hides the .177 caliber barrel’s muzzle, so the gun looks like a .45 Colt. When combined with the slightly shorter forcing cone, the actual internal length of the .177 caliber rifled barrel liner is, wait for it, 6.75 inches (or within a very small fraction of that measurement). So both numbers are technically correct!
If you are wondering about the current 5-1/2 inch barrel length Umarex Colt Peacemaker models, their .177 caliber barrels are recessed 7/16ths of an inch back from the .45 caliber muzzle. Not as deep as the 7-1/2 inch models and their overall exterior barrel length is also about 1/16th of an inch short of a .45 Colt 5-1/2 inch barrel. If you look at the box on the 5-1/2 inch models it reads “BARREL LENGTH: 4.5 inches.”
So, Colt Peacemaker fans, take your measurements the same way Sam Colt did back in 1847, from the muzzle opening to the front of the cylinder, and never mind what the box says! We’re talking 19th century authenticity here, not 21st century accuracy.
 Samuel Colt’s Superintendent of the Armory, Elisha King Root, patented a sidehammer revolver with a solid topstrap in 1855, which Colt introduced as the Root 1855 Sidehammer Pocket Model. The small .28 and .31 caliber pistols remained in production until 1870.