Gun Review: Springfield Model 1866

Most major advancements in weaponry owe their existence to war.

The American Civil War, fought primarily with single-shot, muzzle-loading muskets, ended with the U.S. government’s desire to equip its future military with a more efficient and technologically advanced breech-loading arm utilizing the evolutionary, fully self-contained metallic cartridge. Although as many as 19 different types of breech-loading arms were utilized by both sides during this conflict, most were found lacking in reliability and power under combat conditions. This—coupled with the fact that the U.S. government found itself at war’s end in possession of over a million perfectly serviceable, but militarily obsolete, .58 caliber Springfield muzzle-loading rifle-muskets—led the chief of ordnance in mid-1865 to direct the master armorer at the Springfield Armory, Erskine S. Allin, to devise a method for turning these rifle-muskets into breech-loading weapons capable of firing a self-contained metallic cartridge approximating the power of the original Springfield arm. The intent was not only to upgrade and modernize the government’s weaponry, but also to standardize it in terms of weapon type and caliber for use by both infantry and mounted troops alike.

By late 1865, Allin had developed and patented his system for converting the front-loading Springfield to a breech-loader by use of a hinged breechblock that fit into a milled-out recess at the musket’s breech and was held in place initially with a single screw and solder. This hinged breechblock was designed to tip up and forward upon opening, exposing the chamber for loading and unloading, and it was held closed for firing by a thumb-operated cam latch located at the rear and right side of the block. Because of the way it looked and operated, this system became known as the “Trapdoor” Springfield.

This conversion, designated the “U.S. Rifle Model 1865,” used a newly developed, copper-cased, rimfire cartridge designed to utilize the musket’s original bore size of 0.58 inches, firing a 480-grain, conical-shaped bullet propelled by a 60-grain charge of black powder. This resulted in a muzzle velocity out of the Springfield’s original 40-inch barrel of some 1,150 fps. A trial lot of 5,000 Allin conversions were built, but subsequent field-testing revealed several deficiencies in both arm and ammo.

Based on the recommendations from its testing in the field, several modifications were undertaken on the Model 1865 and introduced a year later, resulting in the 2nd Model Allin conversion, or the Model 1866. Most notably was its caliber change from .58 rimfire to .50 centerfire. To accommodate this smaller caliber, original .58 caliber 1863 musket barrels were drilled out to accept a steel or iron tube, which was brazed in place and then rifled. This new centerfire cartridge fired a 450-grain lead projectile propelled by 70 grains of black powder to a velocity of around 1,240 fps. It became known as the .50-70 Government. Although both the 1st and 2nd Model Allins were often recorded as having 40-inch barrels—the length of the original Civil War barrels from which they were made—the actual barrel length, when properly measured from the muzzle to the new breech face in the Model 1866, was 36-5/8 inches. This change in caliber resulted in an arm not only more accurate than its predecessor, but also one capable of a much flatter trajectory as well.

Gun Details

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I was recently fortunate to loan a really nice Springfield Model 1866 for this article. According to all of the literature I’ve consulted, this rifle is in “as-issued” condition, having all of the characteristics of this limited-production arm. Like the Model 1865, the Model 1866 was unserialized, yet I was able to pinpoint its date of manufacture as being within a two-year period due to the fact that it was only made during 1866 and 1867 when, based on additional changes, it morphed into the Model 1868. Trapdoor conversions from the Model 1868 on were serialized.

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My loaner rifle is in remarkably good shape for its age. Its barrel measures exactly 40 inches overall when the portion occupied by its new breechblock is included in its measurement, or right at 36-5/8 inches when a tape is dropped down its muzzle until it contacts the face of its new breech. A close look of the muzzle of this arm confirms the presence of the liner that was used to reduce the size of its original bore from .58 to .50 caliber. The inside of the barrel on this particular rifle is in amazingly good shape, showing strong three-land and three-groove rifling, and there are only a few areas of light pitting in an otherwise shiny bore.

As is common to this model, the barrel is secured to the stock using three oval barrel bands held in place by band springs. A sling swivel is attached to the center band and is used in conjunction with a second swivel affixed to the front of the triggerguard bow. The finish on all mountings and other metal parts, save for its new breechblock, lock and hammer, remain “National Armory bright” (brightly polished), as found on the original 1863 musket. Its new breechblock, although now shiny, retains little of its original black finish caused by its casehardening and quenching in oil. Much of this black finish, however, remains on the underside of the block. The lockplate and hammer originally wore bright, colorful casehardening, created by its quenching in water, but this has long disappeared due to use and the passage of time.

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The year “1866” and a bird are stamped on top of the rifle’s breechblock, just ahead of the trapdoor’s hinge.

Markings on the 1866’s breechblock include the year 1866 and an eagle’s head located just behind the hinge. The front part of the hinge is fastened to the barrel using two screws as well as soft soldering. The 2nd Model Allin’s lockplate retains its standard Civil War markings of an eagle and “U.S. Springfield” in front of the hammer and the year 1864 stamped to the rear of its hammer.

The Model 1866 wears a two-piece triggerguard assembly—typical for this vintage Springfield—and its trigger is smooth-faced. A screw-in, metal-slotted ramrod rides in a trough in the stock below the barrel. The American walnut stock on the Model 1866 (donor wood from earlier arms) is of the full-length military pattern, coming to within about 3 inches of the muzzle and ending in an iron forend cap. A cartouche bearing the initials of Erskine S. Allin is still readable on the left side of the stock, just behind the rear lockplate screw. The buttstock ends in a U.S.-marked iron buttplate. The wood on my loaner rifle is still quite sound and devoid of any cracks or major dings.

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The Model 1866 featured a two-position rear sight with an aperture blade that was easy to raise and lower

The sights on the Model 1866 consist of a rear folding leaf, with both open notches and apertures, paired to a front blade on a stud that also serves as the anchor for a triangular Civil War-pattern bayonet. The overall length of the Model 1866 measured 55-7/8 inches, and it weighed in at 9.4 pounds unloaded. The trigger broke with just a little creep at a manageable 5 pounds. This is a nicely preserved example of a Model 1866, and I was looking forward to shooting it.


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The .45-70 cartridge (left, with bullet) replaced the Model 1866’s .50-70 (right) in U.S. military service in 1873.

Developed in 1866 at the Frankford Arsenal especially for the 2nd Model Allin conversion, the .50-70 Government was the first centerfire cartridge to be put in general use by the U.S. military, and it remained the official U.S. chambering from its introduction in 1866 until it was superseded in 1873 by the .45-70 cartridge. In its original form, the .50-70 fired a 450-grain lead bullet powered by 70 grains of black powder, producing a velocity of around 1,240 fps from the long barrel of the Model 1866.

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Fortunate for me, the owner of my loaner rifle also provided me with loading dies, cast bullets, a wad punch and some recently manufactured, unprimed .50-70 brass cases. Although this round has been technically obsolete since the turn of the 20th century, reloadable, boxer-primed cases are currently available from several sources like Dixie Gun Works and Starline.

With cases sized and belled, and primed with Winchester Magnum large rifle primers, I added 63 grains (by weight) of Goex FFG black powder to each case using a 30-inch drop tube. I then placed a 0.028-inch cardboard-over-powder wad, punched from writing tablet backing, in each case, over the powder followed by one of the unsized cast bullets I’d been provided. These were cast from a Lyman #509133 mold from a 1-to-20 mixture of lead and tin and weighed 438 grains, measuring 0.512 inches as they came from the mold. Prior to seating, I hand-lubed each bullet with a liberal smearing of SPG bullet lube, ensuring that all three lube grooves were filled. The bullets were then seated to a depth that covered all of the lube grooves and provided for a slight compression of the powder charge, ensuring that all airspace was eliminated within the case.

Range Time

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With a couple of colorful 12-inch bullseye targets set out at 50 yards and the rifle settled into a sandbagged rest, I aligned the sights on my left-sided target. Expecting this rifle to shoot high at this distance, I took a 6 o’clock hold on the bullseye. At the rifle’s report, a big cloud of smoke obscured the target for a few seconds (there was no wind—the blackpowder shooter’s bane), but when the smoke cleared, I could see a rather big hole almost dead-center in my target. Two more rounds formed a most satisfying, perfectly centered 1.4-inch group. A second three-shot group at this same distance measured 1.43 inches. Impressive!

The recoil was nothing more than a modest shove, and the velocities of these first six rounds measured a very consistent 1,227 to 1,242 fps. Using this same 6 o’clock hold, I was able to put three of the 438-grain slugs into a group measuring 4.25 inches at the 100-yard mark. Pretty impressive accuracy for a 149-year-old rifle!

During the seven years it was officially issued by the U.S. Army, the .50-70 cartridge proved to be an effective round. Used during the Indian Wars and by many buffalo hunters, it was also chambered by Remington in its Rolling Block rifles and by Sharps in the conversion of its earlier percussion carbines and later in its sporting rifles. General George Custer and Buffalo Bill Cody were two of its fans.

Although produced for only two years, nonetheless some 25,000 Model 1866s were made. Further improvements on this design led to the Models of 1868 and 1870, and to the introduction of arms configured as carbines and cadet models. It was the platform that introduced the .50-70 cartridge, and it was another step in the evolutionary process that led to the famous Springfield Model 1873 and the .45-70 cartridge it chambered. These remained the official U.S. military long arm and cartridge from 1873 until 1892, when both were replaced by the Krag-Jorgensen bolt action chambered for the .30 Army (.30-40 Krag), the first ever small-caliber, smokeless-powder cartridge ever adopted by the U.S.


This article originally published in the Summer 2015 issue of GUNS OF THE OLD WEST®, print and digital subscriptions to GUNS OF THE OLD WEST are available here.