You are using an outdated browser. For a faster, safer browsing experience, upgrade for free today.
Antique Military Firearms
  • Your shopping cart is empty!

This is an antique 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 a 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 "1863" 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 vast majority of its original color case-hardened finish. The original Hammer is present, and it also retains the majority of its original color case-hardened finish. 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 unmarred with slight pinprick pitting on the face.  The impact surface of the hammer is slightly marred. The Hammer Main Spring is still very strong.

The interior of the lock is in very fine condition and has numerous assembly stamps on the interior of the plate itself.  The Mainspring retains virtually all of its dark oil quenched finish.  The Sear Spring also retains the majority of its oil hardened finish and has a serif “4” inspection stamp on the top leaf.  The Tumbler, Bridle and Sear all retain the vast majority of their original dark oil quenched finish.  The Sear has a serif “H” inspection stamp.  The Tumbler has a “3” inspection stamp and the tumbler lever has a “2” inspection stamp.  The lock functions perfectly.  All internal lock screws are in fine condition.  Both original Lock Plate Screws are present and in fine condition.  The faces of both screws remain in the white with slightly marred slots and the barrels of both screws, including the threads, retain virtually all of the original oil quenched finish.  Both lock plate screw washers are present on the stock, and both remain correctly in the white. 

The original Thumb Latch retains the majority of its original dark oil quenched finish that now exhibits a pewter patina. The top of the Thumb Latch is correctly smooth and the single-slot, rounded head Latch Screw is only 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 all 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 is still smooth with no marring or pitting and it still retains traces of the original oil quenched blackened finish. The bottom of the Breech Block is the straight, cylindrical type that retains 90% of its original, dark blackened oil quenched finish that is beginning to fade towards the top.  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 bottom, interior edge of the breech block has a serif “G” inspection stamp.

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 the majority of its original dark finish. The single-slot Hinge Screw is in good condition that is unmarred with minor pinprick pitting, and it is secured on the left side of the hinge by the original two-part Jam Nut, which also retains the majority of its original finish. The Hinge Strap exhibits a dark, plum patina with minor pinprick pitting towards the rear and both original hinge strap screws are present with minor marring of the slots.  The hinge strap remains tightly attached to the barrel. 

The Stock on this rifle is the original in excellent condition with normal dings and scratches from field use that was lightly sanded in the past.  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 correct oval, script “ESA” cartouche for Erskine S. Allin.   The bottom of the stock wrist, just to the rear of the Trigger Plate, is a script "N" inspection stamp.  The Nose Cap on the Stock is still in its original National Armory Bright finish that is slightly dulled.   The lock mortise is still crisp and there is a serif “W” inspection stamp in the mortise.

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 minor marring of the slot. The Butt Plate itself still retains the majority of its original national armory bright finish with numerous areas of old corrosion on the back and tang portion. 

The Rear Sight on this Model 1866 is the correct US Model 1863/64 Rear Sight from the Civil War. The Model 1866 used the earlier Rear Sight, which was reversed on the new rifle. 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 very good condition and retain traces of the original dark oil finish that now exhibits a plum patina. 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 traces 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 minor frosting in the grooves with strong rifling and a generally shiny finish. 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. 

The Breech of the Barrel shows evidence of use with old corrosion staining.  The Ejector Stud exhibits normal wear.  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.  On the right side of the barrel, just below the rear sight, is a “3” stamp.   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.  The Breech Plug remains in fine condition retaining the majority of its oil darkened finish.  On the back side of the plug are numerous inspection stamps.  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 still retain the majority of their original National Armory Bright finish that exhibits a pewter patina in places along with isolated areas of pinprick pitting.  The original Trigger is present, and it retains 90% of its original oil blackened finish in the protected areas. 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 remains with its National Armory Bright finish with minor dings and evidence of pinprick pitting throughout. The adjacent Band Spring is in very good 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 slightly marred.  The Middle Band has the correct serif "U" stamp on the right side and retains its National Armory Bright finish with minor dings and minor pinprick pitting. The Middle Band Retaining Spring is present and is in good condition. The Upper Band also has the correct serif “U” stamp on the right side, and it retains the majority of its original National Armory Bright finish.  The Upper Band Spring is in fine condition.  The Ramrod is the correct seven cannelure type with slot for cleaning wipes and a cupped end, which is the earlier type ramrod used on the Model 1866 Trapdoor Rifle.  The ramrod still exhibits the majority of its original National Armory Bright finish that generally exhibits a pewter and plum towards the ends. The Ramrod, when stowed, is flush with the muzzle like the earlier 1st Allin Model 1865 Trapdoor alteration rifle. 

This is rare, historically significant, and excellent, 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 functions perfectly.