Making the 3-inch Ordnance Rifle

By the battle of Gettysburg in July 1863, the 3-inch Ordnance Rifle Model 1861 was the most important type of cannon in service with the Army of the Potomac.  Of 372 artillery pieces on the Federal gun lines, 150 were Ordnance Rifles.  An estimated 75 more armed the Confederates on the same field.   By the close of the war Phoenix Iron Works, of Phoenixville, Pennsylvania, delivered 866 examples of this weapon.  Phoenix added 91 more after the end of hostilities before closing production in January 1867.    With such numbers there is little wonder the weapon is familiar to battlefield visitors today.

First Day 10 Aug 08 233
3-inch Ordnance Rifle, No. 233 - The First Shot Gun

The popularity of the Ordnance Rifle stems from its light weight, performance, and durability.  At 820 pounds, the 3-inch Rifle fit the old 6-pdr field gun carriage, although a 12-pdr carriage axle was specified by regulations.  Six horses could easily handle the gun, carriage and limber (with 50 rounds).

The 3-inch rifle fired shell and case shot most often but solid bolts and canister were available.   Tables in the 1864 Field Artillery Tactics manual indicate the rifle, with 16 degrees elevation, could launch a 3-inch Shenkl Shell to a range of 4,180 yards.   First hand accounts laud the weapon’s accuracy.

However what set the 3-inch Ordnance Rifle apart from the contemporary 10-pdr (both 2.9-inch and 3-inch) Parrott Rifles was durability.   Although less expensive to produce, the Parrotts were stigmatized by a propensity to burst, largely with regard to the larger caliber weapons.   But the Phoenix-made guns, by comparison, were nearly free from any reported failures.  The remarkable durability was due to the wrought iron construction technique, first patented by John Griffen, superintendent at the Safe Harbor Iron Works (a subsidiary of Phoenix Iron Works), then later improved upon by Samuel J. Reeves, superintendent of Phoenix Iron Works.

In 1855 when Griffen submitted his patent for wrought iron gun production, memory of the 1844 Princeton disaster and the Stockton Gun was still fresh in the minds.  But Griffen’s approach differed significantly from the earlier use of wrought iron.  Detailed in U.S. Patent Number 13,984, the secret to success was the use of a rolling mill to provide even pressure and thus uniform welds.  Griffen provided this illustration of his technique:

Illustration from Patent Number 13,984

For production of cannon, the foundry started with an iron mandrel as a base (Figure 1 in the illustration).   Griffen described the mandrel as “of round iron about one-half larger than the bore of the cannon intended to be…. Centers are bored in each extremity of this mandrel….”   Note that Griffen is referring to the length of the mandrel when referencing the intended size of the bore.  On that mandrel was placed two rings or “end wings” according to the patent (Figure 3).  Those wings provided alignment and support for a set of faggots or hot iron bars, laid longitudinally along the mandrel forming a “pile” (Figure 4).  Griffen’s patent suggests this pile “… must be such that the outer diameter of the band shall be less than the intended bore of the pile for the cannon.”   Then on top of this pile, a series of hot iron bands were wrapped in a spiral, each layer placed to overlap the seams of preceding layers (Figure 7).  Once the desired diameter was reached, a plug fitted into one end of the mandrel closed the breech and provided metal for the knob.   The mass then was placed between heavy rollers, which by pressure would uniformly weld the bars and bands into one solid form.  The rolling process could even form the required taper, as used on the Ordnance Department’s specified form.  After the rolling was complete, the gunmaker welded trunnions onto the gun tube, and removed the mandrel.

Artillery enthusiasts know well the next part of the story.  The foundry produced cannon for testing at Fort Monroe.  After firing 500 rounds, the weapon was fully tested to destruction using extreme powder and shot loads.  The Army officers requested additional guns for further testing.  Yet even at the eve of the Civil War, in early 1861, the Army was still only requesting examples for further testing.  Not until July 1861 did the Ordnance Department order production for field service.

But the method of production required further refinement.  In order to achieve the desired quality of welds, the foundry workers had to pay careful attention during the entire process.  Apparently, a large number of “piles” were rejected due to openings between the bars.  According to later patent documentation (see link to Number 37,108 below), only one in three piles were accepted for gun production.   The foundry soon replaced the pile of bars with a wrapping of hot sheet iron.  Apparently, concurrent to the work at Phoenix’s foundry, other individuals were also experimenting.  David T. Yeakel of Lafayette, Indiana received Patent Number 35,124 in April 1862, with the following diagram:

Illustration from Patent Number 35,124

Yeakel’s patent involved the use of a cold mandrel, either solid or hollow, around which a sheet of hot iron was rolled.  After the desired diameter was reached, the mass then was placed into a rolling mill which, just as with Griffen’s original technique, welded the joins into a solid form.  Yeakel’s specification called for a mandrel with diameter smaller than the intended bore size.  The entire mandrel was removed or drilled out in the process of finishing the gun.

But this still did not provide the perfect solution to the problem.  At the Phoenix Iron Works, Reeves submitted a his own improvement for patent consideration.  The wording of the application had to address the previous patents issued to both Griffen and Yeakel.  The improvement upon Griffen’s was essentially the same as offered by Yeakel.   But Reeves noted with Yeakel’s solution left a seam that could not be made smooth or sufficiently strengthened with any consistency.   Reeves offered this illustration to support Patent Number 37,108:

Illustration from Patent Number 37,108

Under Reeves’ specification, the mandrel, again either hollow or solid, was not removed after the pile was rolled.  Rather the mandrel remained with the mass and became the inner-most layer of the bore.  Furthermore, Reeves’ method used a heated mandrel that would actually bond and weld to the iron sheet during the wrapping and rolling process.   Note that Reeves used a block, screwed into the mandrel, to form the breech.  And Reeves also welded trunnions on to the gun as specified by Griffen.

The stamp “Patented Dec. 9, 1862” appears on most 3-inch Ordnance Rifles (although only above registry number 236, which is another story for speculation).  The date alludes to Patent Number 37,108 issued to Reeves which outlined the refined method of production.

GB 27 Dec 117
Left Trunnion Marks on a 3-inch Ordnance Rifle

So from review of patent documentation, and to some extent the stampings on the guns, a story emerges.  The famous 3-inch Ordnance Rifle was a product of several years of trial and error, at the cutting edge of technology of the time period.   The product of this gestation period was among the world’s finest muzzle-loading artillery pieces ever made, and sufficiently advanced to give its users (be they Federal or Confederate) an advantage on the Civil War battlefield.


Aside from on site notes, inline citations, and links provided above, sources consulted for this post were:

Hazlett, James C., Edwin Olmstead, and M. Hume Parks. Field Artillery Weapons of the Civil War, Revised Edition. Urbana and Chicago: University of Illinois Press, 2004.

Ripley, Warren. Artillery and Ammunition of the Civil War, 4th Edition. Charleston, S.C.: The Battery Press, 1984.

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Published by Craig Swain

"Historical marker hunter" and Civil War enthusiast.

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