Unit History

The 1/92nd Field Artillery
Association - Vietnam

Back to the Gun

M1A1 Cannon
Technical Data, Specs

By David Powell

Authors Note: When this project was first proposed we felt we wanted to make it simple enough for the average person (and a few of their friends) off the street to be able to walk up to a Howitzer at their local VFW or Foreign Legion Hall and be able to fire off a couple of rounds. So here goes:

By any means necessary, swing the 6½-ton gun around to the proper direction and one of you use the wheelie things on the left side of the cannon back-end to fine tune the direction (up and down, left and right). Then one of you opens up the back-end of the cannon using the handle thingy attached to the barrel plug. Somebody else by now should have a big bullet all put together with one of the right (as opposed to wrong) nose cone things screwed onto the end of it. Stuff it up into the opening so that the brass ring on the big bullet is stuffed up good and tight with those groove things inside the barrel. Be careful of your fingers the big bullets are heavy. Someone else should now have the gunpowder bags ready to toss into the opening. Note; use all of them if you want it to shoot real far and not all of them if you want to shoot closer. The person who opened the barrel end then closes it and puts one of those smaller bullet looking things into the metal clapper thing and screws it into the hole on the back of the barrel plug. You are now ready to fire your first round. Flip a coin to see who gets to pull the pull rope to fire it.

Wait a minute! Did anyone jack the cannon up? Don't forget to jack it up or else you may have to go into the next county to retrieve your cannon if you don't jack it up. The jack is in the front of the cannon and you should crank it down until the wheels are off the ground. Don't let your friends play with rope while you're doing this, who's in charge of this circle jerk anyway. Okay, now I think you are ready to shoot the cannon… a word of caution, the amount of bucking and or movement of the cannon when you fire it is directly proportionate to how hard or soft the ground is and how much gunpowder the guys put into the cannon so you may want to watch out for excessive movement. Don't forget to plug your ears.

Authors Note: As you can see by the above illustration, it's not as easy as it may seem. And though there are many within the Army today as well as within our own organization that may argue the "pure" meaning to the term "Professional Soldier." The young men I served with in Vietnam were all professionals in their own right. So out of respect for all of the Redlegs of the 1/92nd Field Artillery Association, Vietnam and our brothers who have gone to the big Ft. Sill in the sky we are going to do this right. We will try not to bore the reader with too much technical stuff and we will try to explain what we mean and write, if no where else than in the glossary.

Cannon M1A1 (weights & specs):

• Weight of Cannon: 3,750 lbs.
• Caliber: 155mm or 6.102 inches
• Length of bore (in calibers): 23
• Length (muzzle to rear face of breech ring): 149.2 inches
• Travel of projectile in tube: 120.675 inches.
• Rifling: Length: 113.10 inches
• Number of grooves: 48
• Twist: Uniform, right hand, one turn in 25 calibers.
• Type of Breechblock: Stepped Thread, Interrupted Screw
• Muzzle Velocity: 1,850 fps.
• Powder pressure: 31,000 psi.
• Weight of Projectile: 84.80 lbs. (average, varies by type)
• Weight of Powder: 13.91 lbs.
• Maximum Range: 14,600 meters (14.6 kilometers)
• Estimated Life Accuracy: 15,000 rounds
• Estimated Life Expectancy: 7,500 rounds
• Rate of Fire, maximum: 4 rounds per min.
• Rate of Fire, sustained: 1 round per min.
• Recoil at Maximum Elevation: 41 inches
• Recoil at Minimum Elevation: 60 inches
• Range of Elevation: 1,156 mils (65 degrees)
• Rate of elevation per turn of the handwheel: 14.8 mils.
• Range of Traverse: 866 mils (48.7 degrees)
• Rate of traverse per turn of the handwheel: 10.3 mils (34.7 min)
• Traverse to the left of midposition: 418 mils (23.5 degrees)
• Traverse to the right of midposition: 448 mils (25.2 degrees)

Howitzer M114A1 (weights):

• Weight of Carriage (M1A2), complete with Cannon (M1A1): 12,700 lbs.
• Weight of Trail Spade (ea.): 184 lbs.
• Weight of Firing Jack Float: 85 lbs.
• Weight Distribution:
  At end of trails (closed): 540 lbs.
  At right wheel: 6,080 lbs.
  At left wheel: 6,080 lbs.

Misc. information and data:

The external surface of the cannon tube is machined to form a bearing surface, which slides in the recoil mechanism cradle and cylinder yoke during recoil and counterrecoil. Recoil mechanism is of the Hydropneumatic, variable-recoil type, utilizing a floating piston to separate the fluid from the nitrogen. Initial nitrogen pressure at 70° F is 1,650 psi. The recoil cylinder controls the movement of the cannon during recoil and counterrecoil and the recuperator cylinders return the weapon to battery after firing. Recoil varies by elevation. The M1A1 carriage is equipped with a rack and pinion type-firing jack and the M1A2 carriage is equipped with a screw type-firing jack.

The major parts of the Howitzer when viewed from the left front.