UPDATE: Mortar accident theory

People are wondering how so many Marines were injured in the accident in Nevada.

One tantalizing theory goes something like this....

*Marines were performing live fire drills and the tube in question suffered a hang fire (the wording is important here...a misfire is a totally different and somewhat safer beast).

*The Marines failed to properly identify that the weapon suffered a hang fire and the Marines attempted to load another mortar.

*In the process of loading, the first round fired striking the second round which was loaded causing a double feed.

This would explain why the casualties were so high.  Instead of one 60mm round exploding, you had two.

If the reporting is right then this would be the scenario that makes the most sense.

A terrible loss though and my sympathy goes to the families.

NOTE:  Below is a copy of US Army manual FM 23-90 (that the Marine Corps uses) that covers immediate action to be used in case the 60mm mortar malfunctions.

NOTE 1:  Whoever the Range Safety Officer, Range Safety NCO and probably Battalion Commander and Company Commander will probably all suffer career altering letters of reprimand or cautions.  The military can be a rough place during a reduction in force.

3-14. MALFUNCTIONS

Mortarmen must be aware of the following malfunctions.

a. Misfire. A misfire is a complete failure to fire. It can be caused by a faulty firing mechanism or faulty element in the propelling charge explosive train. A misfire cannot be immediately distinguished from a delay in functioning of the firing mechanism or from a hangfire; therefore, it must be handled with care. All firing malfunctions should be considered a misfire. Mechanical malfunctions can be caused by a faulty wiring pin or by rounds lodged in the barrel because of burrs, excess paint, oversized rounds, or foreign matter in the barrel. Procedures for removing a misfire are discussed in paragraph 3-15.

b. Hangfire. A hangfire is a delay in the functioning of a propelling charge explosive train at the time of firing. In most cases, the delay ranges from a split second to several minutes. Thus, a hangfire cannot be distinguished immediately from a misfire.

c. Cookoff. A cookoff is a functioning of one or more of the explosive components of a round chambered in a hot weapon, initiated by the heat of the weapon.

3-15. REMOVAL OF A MISFIRE

The procedures for removing a misfire are different for handheld and conventional modes. The propelling charge may not function for the following reasons:

• Defective ignition cartridge.
• Defective, damaged, or loose firing pin.
• Fouled firing pin or firing pin obstructed by extraneous material.
• Fouled bore.
• Excess oil or water in the bore.
• Misaligned stabilizing fin.
• Foreign matter or excess paint on round.
• Selector switch on SAFE or TRIGGER.

a. Conventional Mode.

(1) When a misfire occurs, any member of the squad immediately announces, "Misfire." The entire squad stays with the mortar. If it is obvious to the squad leader that the round has reached the bottom of the barrel and it has failed to ignite, the gunner places the selector switch on trigger fire and squeezes the trigger several times to try to clear the round.

WARNING During peacetime live-fire training, the ammunition bearer moves at least 50 meters to the rear of the mortar.

Notes:	1. A faulty firing pin assembly on a 60-mm mortar, M224, requires that the firing pin be tightened upon completion of firing when frequent trigger firing using M720-, M721-, or M722-series ammunition. These type rounds usually fire when trigger fired.
	2. In case of a hangfire, kick the cannon several times to dislodge the round.

CAUTION Trigger fire the M720-series rounds with charges 0 and 1 only. If an emergency requires trigger fire above charge 1, the baseplate must be well seated and extreme caution taken.

(2) If the round fails on trigger fire, the gunner places the selector switch back on drop fire. Staying clear of the muzzle at all times, the squad leader holds the bipod legs to prevent slippage. The gunner strikes the barrel sharply several times with the heel of his boot just above the handle assembly. If the round fails to dislodge after trigger firing and kicking, the gunner places the selector switch on SAFE.

WARNING During peacetime live-fire training, the gunner and squad leader join the ammunition bearer and wait one minute (in case of a cookoff). After waiting one minute, the gunner returns to the mortar.

(3) The gunner checks for heat by starting from just below the muzzle and working down to the base with his fingertips. If the barrel is too hot to be handled, he cools it with water (or snow) and checks it one minute later. If no water (or snow) is available, the barrel is air cooled until it can be easily handled with bare hands.

Notes:	1. Liquids must never be poured into the barrel.
	2. During peacetime live-fire training, the gunner signals the squad leader to come forward once the barrel is cool.

(4) The gunner locks the data down on the sight, then removes the sight and places it in a safe location. He then lowers the barrel to its minimum elevation and backs off one-quarter turn. DO NOT MOVE THE BIPOD LEGS OR CHANGE THE FIRING SADDLE DURING THIS PROCEDURE. The gunner unlocks the barrel from the baseplate by loosening the locking knob until the barrel can be rotated. He rotates the barrel 90 degrees in the socket cap so that the flats on the barrel are aligned with the flats of the socket cap. The squad leader places his left leg in front of the nonmechanical leg of the bipod to keep the bipod steady during the misfire removal. After placing his leg in this position, the squad leader places his left hand near the top of the barrel and his right hand on the underside, just below the muzzle. He prevents any part of his body from passing in front of the muzzle.

WARNING Once the barrel reaches the horizontal, it must not be lowered back down until the round is extracted. If the round slips down the barrel before extraction, it could ignite, causing death or personal injury.

(5) The gunner continues to raise the barrel so that the base of the barrel is higher than the top. With the muzzle pointing toward the ground, the gunner shakes it slightly to help dislodge the round. As the round starts to clear the muzzle, the squad leader squeezes his thumbs against the body of the round--not the fuze--and removes it. If the round fails to come out once the barrel is lifted, the barrel is lowered back to the horizontal. It is removed from the bipod assembly and placed in a designated dud pit. EOD personnel are notified for removal or disposal.

(6) Once the round has been removed, the squad leader gives the round to the ammunition bearer who inspects it. The ammunition bearer replaces any safety pins and inspects the primer of the ignition cartridge. If dented, the round should not be fired. If the primer has not been dented, the firing pin on the mortar should be checked for proper seating and tightened down if needed.

(7) While the round is being inspected, the gunner lowers the barrel back into the baseplate and remounts the sightunit to the bipod. The ammunition bearer then swabs the bore, and the gunner re-lays the mortar on the previous firing data.

Note:

If the baseplate moved during the misfire procedure, the mortar must be reciprocally laid.

(8) If the primer on the round has not been dented, the gunner tries to fire the round again. If the same round misfires, he repeats the misfire procedures. If the primer has been dented, he notifies organizational maintenance IAW unit SOP.

b. Handheld Mode.

(1) When a misfire occurs, any member of the squad immediately announces, "Misfire." The entire crew stays with the mortar, and the gunner immediately pulls the trigger twice. If the round still fails to function, he announces, "Misfire." The gunner places the selector switch on SAFE and bounces the mortar from at least 6 inches off the ground to dislodge the round. (Disregard if the crew heard the round strike the bottom of the barrel.)

WARNING During peacetime live-fire training, the gunner stays with the mortar and all other crew members move at least 50 meters behind the mortar.

Note:

The gunner bounces the mortar only if the round is between the muzzle and firing pin.

(2) The gunner places the selector switch back on trigger fire and squeezes the trigger twice--the mortar should fire. If the round does not fire, he places the selector switch on SAFE and supports the mortar barrel with sand bags, logs, or empty ammunition boxes to keep the barrel upright and stable. He ensures the barrel is up and pointing downrange. The gunner checks for heat with his fingertips only, starting just below the muzzle and working down to the base.

WARNING During peacetime live-fire training, the gunner joins the rest of the squad and waits one minute.

(3) If the barrel is hot, the gunner cools it with water (or snow) and then rechecks for heat. If there is no water (or snow), he lets the barrel air cool until it can be easily handled with bare hands.

Note:

During peacetime live-fire training, the gunner signals the squad to come forward once the barrel is cool.

(4) Once the barrel is cool, the squad leader places his left hand (fingers and thumb extended and together) near the top of the barrel and his right hand on the underside just below the muzzle. In one smooth motion, the gunner lifts the base of the mortar with the M8 baseplate to the horizontal position. Once the barrel reaches the horizontal position, the squad leader extends the meaty portion of his thumbs over the end of the muzzle. The gunner continues to raise the base of the barrel past the horizontal. With the muzzle pointing downward, the gunner slightly shakes the barrel to help dislodge the round. As the round starts to clear the muzzle, the squad leader catches the round by squeezing his thumbs against the sides of the body--not the fuze--and removes it. The squad leader passes it to the ammunition bearer. If the fuze has safety pins (other than the M734), he tries to replace them.

(5) The ammunition bearer inspects the primer of the ignition cartridge. If dented, he does not try to fire the round again. If the pins cannot be replaced, the fuze may be armed. He lays the round in the designated dud pit and notifies EOD personnel.

(6) If the round does not come out after lifting the barrel up and shaking it, the gunner returns the barrel to the horizontal. The squad leader places the barrel in the designated dud pit and notifies EOD personnel.

WARNING Once the barrel reaches the horizontal, it must not be lowered back down until the round is extracted. If the round slips down the barrel before extraction, it could ignite, causing death or personal injury.

(7) If the primer on the round has not been dented, the gunner lifts the base as high as possible. He shakes the barrel to dislodge any debris and swabs the bore. He tries to fire the round again. If two misfires occur in a row without the primer being dented, the gunner notifies organizational maintenance IAW unit SOP.