In the aftermath of the bloody Civil War the newly reunified United States found itself needing to adopt a modern breechloading cartridge arm, and began to explore a solution using the surplus of rifled muskets left over from the conflict.

The History

A year after the end of the American Civil War the newly reunified United States found itself both secure in the knowledge that breech loading cartridge arms were the way of the future, as well as an enormous inventory of new or nearly new rifled muskets. The Model 1861 Springfield musket had been the most common arm in the hands of Union forces during the war, with upwards of one million produced in the four year span of the war.

Despite the ubiquity of the Springfield, breech loading cartridge arms and even some repaters, such as the Spencer and Henry rifles had seen service, clearly demonstrating their superiority to the US Ordnance Board. With testing initiated of various models of breechloader after the end of the war, the design submitted by Erskine Allin of Springfield Armory for a simple conversion of the existing stocks of muskets interested the now cash strapped post-war War Department.

The front sight (which doubles as a bayonet lug) and cleaning rod are virtually indistinguishable from the earlier Springfield Musket

The original Model 1865 fired a rimfire .58 caliber cartridge, and was accomplished simply by cutting out the top of the breech and installing a block assembly, its method of swinging open lending the name “Trapdoor” to what would become a family of rifles. Despite the economy and utility of the design, some issues persisted, and it was an improved Model 1866 that was accepted for general issue the following year.

This conversion included sleeving the barrel to accept a new .50/70 cartridge and improvements to the ejector on the trapdoor. Despite some controversy in its adoption, it began to be issued as the first standardized centerfire cartridge arm of the United States. The design would see action mainly in the Indian Wars as the Civil War gave way to the Old West, notably ensuring victory in the Wagon Box Fight and Hayfield Fight in 1867, as Souix attackers were surpirised by an enemy they thought were armed with muskets.

The rear sight is also essentially the same as that on the M1861 Musket, having been replaced with a slightly different leaf set for the .50/70 cartridge

Despite this success, the Springfield was still problematic, and only lasted for a few years in general issue before replacement with the improved Model 1873 trapdoor in .45/70. The Model 1866 would quickly disappear from service, with a large quantity being sent as aid to France in their doomed 1870 war against the Prussian-led North German Confederation, with the remainder being surplused. One such surplus rifle notably became a favorite of Wild West legend Buffalo Bill Cody, who deemed his rifle “Lucretia Borgia”.

Despite its short service life, the Model 1866 and its predecessor the Model 1865 cast a long shadow across the history of US martial arms. Despite musket conversions being very common in the 1870s, most nations only used them as a stopgap until a better, purpose built design could be adopted, but the United States would begin making the Model 1873 from scratch as a “Trapdoor”, and would skip both the purpose designed breechloader and the black powder repeater entirely, maintaining the M1873 until its replacement with the smokeless, bolt action Krag in 1892.

An overhead view of the new Allin Conversion action, where we can see the trapdoor, modified hammer, latch as well as the dual screws that retain the hinge. Also visible on the hinge is the extractor

The Design

The lineage of the Model 1866 as a rifled musket is obvious from its appearance, with its long barrel and external, hammer fired lock. The conversion entailed cutting off the top half of the barrel just ahead of the breech plug and fitting a small ejector into the bottom of the barrel just ahead of the breechplug.

The new “trapdoor” block is a large milled component that is attached to the barrel by a hinge and two screws. Extraction is accomplished by a simple milled rib on the hinge that interacts with the cartridge rim as the mechanism is opened. A new hammer was also installed, curving farther over the action to strike the new firing pin, which runs diagonally through the breechblock. A spring loaded latch in the place of the old nipple allows for opening of the breech, with the hammer in either the full or half cock position.

With the action open the origin of the origin of the “Trapdoor” moniker becomes apparent

This Example

The example seen here is in overall very good condition, with its original bright finish still apparent throughout as well as good rifling. The weapons was made in 1866, and uses an 1864 dated Springfield lock, as is common with these conversions. The wood stock is also in excellent condition, with numerous cartouches and other markings

The lock of the rifle is in this case a recycled 1864 dated Springfield M1861 lock, with the modified trapdoor hammer attached. The large Federal Eagle is also visible on the plate

Opinions

The Model 1866 is an excellent example of a musket conversion, and is in the opinion of the author a superior design to many of its contemporaries in that category, with a simple but strong mechanism. It was, however, rendered obsolete by foreign designs such as the British Martini, French Gras or even the domestic Rolling Block and Berdan Rifles while it remained in service, and quickly became obsolete even as it and its descendants remained in service for decades.

The .50/70 rifle is an enjoyable rifle to shoot and is capable of impressive accuracy, and is a solid addition to any collection of US martial arms or Western Era firearms.

The upper tang of the rifle’s buttplate also bears the “US” hallmark common of Civil War Era US firearms

Observed Values and Frequency

Updated: July, 2024

AVERAGE VALUE (USD): $800-$1,250

FREQUENCY: Rare

COLLECTOR’S NOTES: Very uncommon compared to later .47/70 models. .50/70 ammunition can be difficult and expensive to source, even including brass for reloading.

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Replica: Mauser M712 Schnellfeuer