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Antique Military Firearms
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This is a fine condition, scarce and original Springfield Armory Model 1866 Trapdoor Rifle, also known as the Second Allin Alteration Rifle, in .50-70 caliber. 


While the American Civil War was predominantly an Infantryman's war using muzzle loading, percussion cap ignition rifles, the use of breech loading, cartridge-firing weapons (principally carbines) left an indelible mark on both the US Army and weapons designers in the United States. The Army's experience during the Civil War left post-war Army leaders with two distinct impressions. First, the accuracy and long-range of modern infantry rifles made the linear, Napoleonic-style of infantry tactics obsolete. And second, the need for faster firing weapons was a necessity for modern infantry combat. The result was the formation of a special board by the War Department to select a new breech-loading rifle. Once the board was formed, it developed a list of requirements for a new breech-loading rifle and sent requests for submissions to all known arms manufacturers and to the National Armory at Springfield. The principal requirements of the new arm were straightforward: a breech-loading firearm chambered for a self-primed, metallic cartridge.

When Springfield Armory received the request for the board, it assigned the responsibility for developing the Springfield design to Springfield's Master Armorer, Erskine S. Allin.  Allin's design was both simple and practical. His design, oddly enough, involved the conversion of the earlier Model 1861 Pattern Rifle Musket that was used during the Civil War instead of the later Model 1863 and 1864 Rifle Muskets. Many thousands of these muzzle-loading rifles were on hand at Springfield after having been returned following the demobilization of the Union Army. Allin's design involved cutting a section out of the breech end of the standard Model 1861 .58 caliber barrel and fitting a hinged breechblock into the cutout space. This was the "trap door" design that became the standard design for the US rifle for the next 25 plus years.

Several foreign and domestic US designs were also submitted to the board in late 1865. The board ultimately chose Allin's Springfield-submitted design. Although many have opined over the years that one of the main reasons for the board's selection of Allin's design was its familiarity to the board's members (it looked very similar to the muzzle loading Model 1861), the real reason probably had more to do with the Army's tiny budget after the end of the Civil War and the relatively low cost of converting existing arms compared to procurement of an entirely new design. The War Department approved the board's recommendation and Springfield was directed to produce 5,000 Model 1865 breech loading rifles, which became known as the "First Allin" Rifle.

The Model 1865 "First Allin" Rifles were finished in 1866 and issued to soldiers in the field. The Model 1865 fired a short, copper-cased, .58 caliber rimfire cartridge with a powder charge of 60 grains and a 500-grain bullet. Reports from these units identified several problems with the new rifles. First, the copper cartridge case had a weak case head that was often torn off during extraction, leaving the rest of the case inside the chamber. Ballistically, the .58 caliber round was also considered underpowered. And the breech system itself was considered too fragile with problematic extraction and ejection components. The problems identified were severe enough that Springfield made the decision to completely redesign the breech action and develop an entirely new round.

The new cartridge that was designed was based around a .50 caliber bullet that had a more pointed tip than the earlier .58 caliber round. The case was also significantly different with a longer overall case length and centerfire ignition system instead of the earlier rimfire design. The new case held 70 grains of black powder, giving the new round a significantly higher muzzle velocity than its predecessor. Springfield also designed a new breech that was stronger and had more robust components.

The new design was, unlike the earlier Model 1864 "First Allin" Rifle, based on the later Civil War issued Model 1863 and 1864 Rifles. The concept was the same, however, in that the rear portion of the original barrel was cut away and the new breechblock was hinged in the "trap door" style. The smaller diameter of the bullet necessitated a more radical change to the existing Model 1863 barrels. The .58 caliber rifled barrels were reamed out along the entire length to a diameter of .640 inches and then fitted with a .50 caliber liner or barrel insert that was brazed in place at the muzzle and breech.

This new rifle was designated the US Model 1866 Rifle, also known as the "Second Allin" Rifle and it performed much better than the Model 1865 First Allin Rifle. The Model 1866 saw active combat service soon after it was issued and was considered instrumental in the Army's defeat of Sioux Indians under Chief Red Cloud at the Wagon Box Fight and Hayfield Fight, both occurring in August 1867 along the Bozeman Trail in the Wyoming and Montana Territories.

The exact number of Springfield Armory manufactured (modified) Model 1866 Rifles is not entirely clear. Norm Flayderman's Guide to Antique American Firearms, the benchmark text on American weapons, states that only about 25,000 were manufactured. Richard Hosmer's fine work on .58 and .50 caliber Springfield Rifles lists approximately 52,300 Model 1866 Springfield Rifles manufactured with most produced in 1867, plus a few hundred additional rifles in 1868 and 1869. Regardless of the total number made, which is still a small number comparatively speaking even if Hosmer's number is used, when the Model 1866 was eventually replaced a few years later with the US Model 1868 Rifle, most of the existing Model 1866 Rifles were purchased by the Remington Arms Company and were resold to the French for use during the Franco-Prussian War of 1870-1871. While some of these rifles made it back to the United States over the years, the majority did not, making the Model 1866 a historically significant and very scarce example of American military firearms design.

As noted, this particular Springfield US Model 1866 "Second Allin" Trapdoor .50 caliber Rifle is in fine, original condition. The Lockplate is the correct Civil War era Model 1863/64 Lockplate that is correctly marked "1864" to the rear of the Hammer. Forward of the Hammer is the federal spread eagle with the eagle looking towards the muzzle. The eagle bears the large shield and the detail is still exceptionally fine. Just forward of the eagle is a crisp, serif "U.S./SPRINGFIELD" stamp.

The outer, flat surface of the Lockplate still retains the majority of the original color case-hardened finish with even more present on the edges.  The original Hammer is present, and it also retains most of its original case-hardened finish with wear noted on the sharp edges. The in-shield knurling on the thumb piece of the Hammer is still crisp. The face of the Hammer, correctly, comes together with the rear of the Breechblock comb to form a line that is not perpendicular to the barrel, which makes the Model 1866 unique among all Trapdoor models. The original single-slot, rounded face Hammer Screw is present and is in fine condition and is unmarred. The Hammer Main Spring is still very strong.

The interior of the lock is also in very fine condition and retains the majority of its original color case-hardened finish.  The interior of the lock plate has numerous inspection stamp.  The Mainspring retains virtually all of its oil-hardened finish and remains strong.  The Sear Spring also retains the majority of its original oil-hardened finish and has a “3” inspection stamp on the top leaf.  The Tumbler, Bridle and Sear all retain the vast majority of their original dark oil quenched finish.  The Tumbler Rocker Arm has a “5” stamp.  The Tumbler has an “8” stamp.  The Sear has a “1” stamp.  The lock functions perfectly.  All internal lock screws are in fine condition.  Both original Lock Plate Screws are present and are in fine condition.  Both lock plate screw washers are present on the stock and both remain correctly in the white that now exhibits a slight pewter patina. 

The original Thumb Latch retains the majority of its original dark oil-quenched finish with areas of wear. The top of the Thumb Latch is correctly smooth and the single-slot, rounded head Latch Screw is unmarred. The Thumb Latch is the second of two types used on the Model 1866, with the integrated, machined cam. The Cam Cap and single-slot Cam Latch Screw are in fine condition retaining most of their original blackened oil quenched finish.  This second type of cam was introduced at around production number 7,000.

The Breech Block is the correct type with the flat-top firing pin housing or comb. The top surface of the Breech Block still retains considerable original oil quenched blackened finish with minor surface corrosion present. The bottom of the Breech Block is the straight, cylindrical type that retains 95% of its original, dark blackened oil quenched finish. There is a serif “Z” inspection stamp on the bottom of the Breech Block. The top, forward section of the Breech Block has a crisp "1866/small eagle head" stamp. There is, correctly, no sighting notch in the Breech Block Hinge, which is also unique among Springfield Trapdoor weapons.

The Breech Block opens the full 160 degrees, which is far more than any other Trapdoor Breech Block. The Firing Pin, which is retracted by a Firing Pin Spring that is still strong, is secured at the end of the comb by a Spanner Head Retaining Collar, which retains traces of its original dark finish. The single-slot Hinge Screw is in good condition with minor marring and is secured on the left side of the hinge by the original two-part Jam Nut, which also retains the vast majority of its original finish. The Hinge Strap is in fine condition and retains the majority of its original, but now thinning, oil blackened finish. Both single-slot Hinge Strap Screws are present and are in excellent condition.

The Breech Block Retaining Plate and Screw are in very fine condition and exhibits a pewter patina.  The Horseshoe Spring retains almost all of its dark oil finish and remains strong.  The Long Spring retains the majority of its original dark oil finish and the Long Spring Screw still retains traces of its tempered blue finish.  


The Stock on this rifle is the original in excellent condition with normal dings and scratches from field use.  Model 1866 Rifles used one of two types of stocks. The first were existing US Model 1863/64 Civil War-era stocks that were subsequently modified to accommodate Erskine Allin's mechanism. The second type of stock was a new, black walnut stock that was milled from a stock blank especially for the Model 1866 Rifle and its unique mechanism. This particular stock is the earlier, Civil War Model 1863/64 Stock that was modified.  On the left stock flat is the oval-end, boxed cartouche with script letters "HSH" inside the box. The "HSH" initials stand for Springfield Armory Inspector, H. S. Hill. The cartouche measures approximately .67" by .25".  Below the “HSH” cartouche is the oval “ESA” cartouche of Erskine S. Allin.  The bottom of the stock wrist, just to the rear of the Trigger Plate, is what appears to be a serif, "R" inspection stamp. The Nose Cap on the Stock is still in its original National Armory Bright finish that is slightly dulled.  The original Nose Cap Screw is present, and it retains the majority of its original dark oil finish with an unmarred slot.

As noted, this is the earlier type of stock used on Model 1866 Rifles, utilizing existing Civil War rifle stocks.  The original inlet for the ramrod friction spoon is still present, as is the original pin, and there is the correct additional inletting for the horseshoe spring and the long spring.  The lock mortise is still crisp.

The Butt Plate is the correct and original curved profile, convex surface type with crisp "US" stamp on the Tang. Both the Tang Screw and Butt Plate Screw are the correct single-slot, rounded face type that are in good condition with no marring of the slot. The Butt Plate itself still retains traces of its original national armory bright finish with the bulk of the butt plate exhibiting a plum and pewter patina.

The Rear Sight on this Model 1866 is the correct US Model 1863/64 Rear Sight from the Civil War. The Rear Sight Base is attached to the top of the barrel in a dovetail and is held in place by its original Spanner Head Screw, and this Screw and the "floor" of the Rear Sight Base in which the Spanner Nut secures the sight are both in fine condition and are in the national armory bright finish. The Elevation Leaf is correctly marked for 100, 300 and 500 yards with a 700-yard notch at the top of the Leaf. The Elevation Leaf retains the vast majority of its original blued finish. The Leaf Screw secures from the left side and the Leaf Screw's single-slot is unmarred.

The Barrel on this Model 1866 Rifle is the original modified .58 caliber Model 1863 muzzle-loading Barrel that is 40" long. The Model 1863 Barrels used on the Model 1866 Rifles were reamed out to a diameter of .640" the entire length of the Barrel and were then fitted with a .50 caliber, rifled Barrel Liner that was brazed at the end and the Barrel crowned. The braze line on this Barrel is barely noticeable and the Liner is still secure. The bore has the 3-groove rifling and the bore exhibits very minor frosting in a few small places, but it generally presents a mirror finish with strong rifling. The original Front Sight is present and is still securely brazed to the top of the Barrel. The external surface of the barrel remains in its original bright finish with only very minor areas of staining.  The barrel is in fine condition.

The Extractor Arm portion of the Breech Block exhibits normal wear from use. The Thumb Latch Cam Recess in the end of the Barrel is smooth. The original Nipple Recess Filler, which was done on all modified Barrels to fill in the area of the Barrel that held the nipple and bolster, is present and the weld seams are in very fine condition. The left barrel flat has the correct, full eagle head stamp from its original Civil War proofing. The eagle stamp is still crisp. On the lower left side of the barrel is a serif “M” stamp and a serif “TE” stamp.  On the left side forward of the spring is a serif “D” stamp.   On the lower right side of the barrel, on the flat, is a serif “D” stamp and there is a serif “S” stamp just to the rear of the bolster recess.

The Barrel Tang is still in National Armory Bright and is very clean and the single-slot, flat head Tang Screw is in excellent condition with only a slightly marred slot.  The Breech Plug remains in very good condition retaining the majority of its oil darkened finish.  On the back side of the plug are two inspection stamps, an “&” stamp and a “1” stamp.  On the back of the barrel are numerous inspection stamp letters and numbers, both from the original Civil War manufacture and during the alteration. 

The Trigger Guard and Trigger Plate assembly remain with their original National Armory Bright finish that is now largely a pewter and plum patina.  The original Trigger is present, and it retains 95% of its original oil blackened finish throughout. The Trigger operates smoothly and still releases the Hammer crisply. The original Lower Sling Swivel Assembly is present along with the Lower Sling Swivel Screw.  Both Trigger Plate Screws, which are round head, single-slot Screws, are present and both are unmarred.

The Lower Barrel Band has the correct, serif "U" stamp on the right side and retains traces of its National Armory Bright finish with minor dings. The adjacent Band Spring is in fine condition.  The Middle Barrel Band has the original Sling Swivel present and attached with a correct Split Shank Swivel that is retained by a flat head, single-slot Band Screw that is unmarred. The Middle Band has the correct serif "U" stamp on the right side, and it retains generous traces of its original bright finish. The Middle Band Retaining Spring is present and is in fine condition.

The Upper Band also has the correct serif “U” stamp on the right side, and it retains most of its original National Armory Bright finish with areas of plum staining.  The Upper Band Spring is in fine condition.  The original slotted-head Ramrod is present and is 38 3/4" long and it retains its National Armory Bright finish that generally exhibits a pewter patina throughout. The Ramrod, when stowed, is correctly 1 1/8" short of the muzzle. 

This rifle comes with an original and rare leather rifle sling.  The Sling is secured to the rear sling swivel assembly by a brass stud.  The other end of the sling has the two-hook brass claw attachment.  Both original stitched keepers are present.  The sling exhibits some crazing but still remains very supple. 


This is rare, historically significant, and fine, original condition example of the Springfield US Model 1866 "Second Allin" Conversion, .50-70 caliber Trapdoor Rifle that is in its 100% original configuration. This Model 1866 Rifle is in firing condition.