Rather than the sliding breech block engaging the breech face of the barrel at a 90-degree angle, perpendicular to it, they inclined the breech 22 degrees to the rear, resulting in an operating angle of 112-degrees. This inclined plane is clearly evident from the exterior of the gun, as the breechblock is obviously canted to the rear. The M-1851 series of gun utilized the Maynard Priming system and had a unique “box lock” mechanism, with the hammer inside the lock plate, rather than outside the lock. This allowed the bottom portion of the hammer to serve as the tumbler upon which the hammer operated, rather than having a separate tumbler inside the lock that connected to the hammer outside the lock.
The M-1851 was produced from November 1 of 1852 through April 1 of 1855 and based upon factory serial number records a total of about 2,050 M-1851 were produced. Only 193 were sporting rifles and the balance were carbines. Of the carbines, 150 were delivered on a US Army contract for use by the U.S. Dragoons in Texas and New Mexico. Another 60 were delivered on a Navy contract. They were produced with the typical 21” round carbine barrels. Most were mounted with some variant of a sling bar for mounted carry. Both carbines and sporting rifle variations were produced in .38, .43 and .52 calibers.
The sporting carbines and rifles were offered with either round or octagon barrels in lengths ranging from 18” to 34”, with 27” being the “standard” and most commonly encountered length. All were brass mounted with brass patchboxes and buttplates standard and brass barrel bands on most carbines. ( a limited few were produced without patchboxes)
The rifles typically had pewter forend caps, but some were made without them as well. The standard sights were a fixed front and folding “squirrel tail” shaped rear mounted on the barrels of both rifles and carbines. On the carbine a fixed brass blade was the standard front sight and a fixed globe front sight was standard on the rifles. An additional folding long-range sight was typically mounted on the receiver tang of the rifles as well.
Of course special order sights were available for the sporting arms, and both sporting rifles and carbines were available with factory embellishments like high grade wood, standard engraving, “extra” engraving, etc.