Hvy.Arty 4.5 inch Siege Rifle

The 4.5 inch Siege Rifle is a large siege and garrison gun that actively served in Union Field Artillery batteries, and had a reputation for being easy to transport, more reliable than the 20 pdr. Parrott Rifle and 800 lbs. lighter than the 30 pdr. Parrott Rifle

The Siege Rifle was sometimes mistakenly called a 4.5 inch Ordnance Rifle or 4.5 inch Rodman Rifle because of it's shape. However, it did not use the welded wrought iron construction of the 3-inch ordnance rifle, nor the hollow casting process used to make Rodman guns. Instead it was made from a conventional solid cast iron gun block, bored and then rifled. It's shape is deliberate and designed to minimize failures from "planes of weakness".

  • Type: Muzzleloading Rifled Siege Gun
  • In Service With: U.S. Army
  • Purpose: Siege Operations & Limited Long Range Field Work
  • Developed By: U.S. Ordnance Department
  • Rarity: Rare
  • US Casting Foundry: Fort Pitt Foundary, PA
  • Years of Manufacture: 1861-1866
  • Tube Composition: Cast Iron
  • Purchase Price in 1863: $0.13/lb. or $448.50 (US)
  • Variants: None
  • No. Purchased During the Civil War : 113
  • No. of Surviving Pieces Today : 56
  • Bore Diameter: 4.5 inches
  • Bore Length: 120.0 inches
  • Rifling Type: 9 rifle grooves 0.10 inches deep, Uniform Right Hand Twist, 1 turn in 15 feet
  • Trunnion Diameter: 5.3 inches
  • Barrel Thickness: at small of Muzzle - 2.25"; near Vent - 5.75"
  • Tube Length: 133 inches
  • Tube Weight: 3,450 lbs.
  • Carriage Type: No. 2 Siege Carriage (2,300 lbs.)
  • Total Weight (Gun & Carriage): 5,750 lbs. (2.8 tons)
  • Horses Required to Pull: 8
  • Standard Powder Charge: 3.25 lbs. Cannon Grade Black Powder
  • Projectile Types: Hotchkiss, Dyer, and Schenkl Shells
  • Projectile Weights: 25 to 32 lbs.
  • Rate of Fire: 12 to 20 rounds an hour
  • Effective Range (at 5°): 2,100 yards (1.19 miles)
  • Max Effective Range (at 10°): 3,265 yards (1.85 miles)
In addition to its use as siege artillery, two batteries of 4.5-inch Siege Rifles, 8 guns total, accompanied the Army of the Potomac as “heavy” field artillery between 1862 and 1864. The big guns were intended for long range firing against Confederate artillery. Although the guns showed very good mobility, they saw very limited action.

Regarding the usefulness of the 4.5 inch Siege Rifle, while detailing siege operations in the Richmond area, Henry L. Abbot wrote, "The two siege batteries of 4.5 inch Ordnance guns, which accompanied the army of the Potomac in all its movements from Fredericksburg until the final crossing of the Rapidan, were of great use, from their superior range and accuracy, in silencing troublesome field batteries and in other field service; and could be moved with the reserve artillery without impeding the march of the army."

The only problem that periodically cropped up with this gun was that it suffered from excessive enlargement of the vent caused by the hot gasses rushing through the vent when the gun was fired. The vent could become too large to fire the piece after about 400 discharges. To fix this problem, the gun crew could be installation a copper vent piece called a bouché.


Three 4.5 inch Siege Rifles of 1st Connecticut Battery at Stafford Heights,
on the banks of the Rappahannock River, overlooking the town of Fredricksburg.
These rifles are in their traveling position, with implements loaded and trails connected to the limbers. .

Last edited:


2nd Lieutenant
Aug 3, 2019
An interesting point about the use of bouches. de Tousard had a lengthy discussion of vents and the proper dimensions of bouches for field artillery (down to 4 pounders) in his 1809 manual for the US.

James N.

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Here are a pair I photographed at Alexandria, Virginia's Fort Ward restoration during a visit in August, 2014; the one in the foreground is positioned on its carriage for transport.


Lieutenant General
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Apr 1, 1999
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View attachment 340423

Here are a pair I photographed at Alexandria, Virginia's Fort Ward restoration during a visit in August, 2014; the one in the foreground is positioned on its carriage for transport.
This is an operation I’d love to shoot a YouTube video on, moving the barrel looks hard, but I looked at Smithgall’s gun, he has the tools to do the movement including the roller that goes under the barrel, it might actually be pretty easy with enough men.

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