Clearing of Live Ammunition from Guns, NAVWEPS OP 1591, 1961, describes the safe methods of clearing live ammunition from guns.
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The purpose of this publication is to direct the precautions and procedures to be followed in removing live ammunition from naval gun barrels.
2. SUMMARY
Live ammunition left in a gun barrel is a potential source of danger to the ship, its equipment and crew. Any attempt to remove ammunition components from a gun barrel through the breech involves an element of risk. In general, the procedure is to clear the gun by firing it whether the projectile is fully seated or not. Firing is sometimes prevented by mechanical difficulties or tactical considerations in which cases the ammunition components must be unloaded through the breech. If the gun is hot and unloading cannot be accomplished immediately, then adequate cooling must be provided to avoid an explosion. Proper safety precautions must be observed at all times to
reduce the possibility of an explosion.
Information contained in this publication has been obtained from past experience and tests. Many activities through long experience, have established their own procedures for clearing live ammunitions from guns. Exact compliance with the procedures outlined in this publication therefore, is, not directed; but the reason for departure therefrom should be justified carefully by the activity concerned. Such activities should inform the Bureau of Naval Weapons of their reasons for such deviations so that new information may be made available for use in any future revision of this publication. Supplementary information, which must be thoroughly studied and understood, is contained in the applicable publication for the gun and in NAVORD INSTRUCTION 5100.1 (Safety Precautions). Barrels have bulged, housings have burst and many casualties to personnel have occurred through ignorance of the correct procedures and precautions for unloading.
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Chapter 2 GENERAL DESCRIPTION, PRECAUTIONS AND PROCEDURES
1. PREFACE
This publication presents procedures and precautions to be followed when unloading ammunition from gun barrels. For detailed operational characteristics of any specific gun, refer to the Ordnance Pamphlet for that gun and use it in conjunction with this publication.
2. DEFINITIONS
Ammunition may be left in a gun because of mechanical failure of the gun, an order to cease fire after the gun has been loaded, or faulty ammunition performance while firing. In such cases certain conditions of the gun and ammunition components will determine the procedure to be followed. These conditions must be known and are herein defined.
a. COLD GUN. Except for 20-mm and smaller calibers, a cold gun barrel is one on which the bare hand can be placed, anywhere on the outside surface, without discomfort. This applies unless stated otherwise in the specific chapter concerning a particular gun. This does not apply to the 40-mm water-cooled barrel or the 3"/70 which has a cooling jacket over its entire length.
b. HOT GUN. The definition of a hot gun barrel varies with the caliber. On the basis of experience and data obtained at the Naval Weapons Laboratory, the following definitions have been established. Any gun that exceeds the firing schedules listed shall be considered a hot gun
until next adjudged to be cool. In general the muzzle is the hottest part of the exterior barrel surface.
(a) Air-Cooled. When more than 75 rounds have been fired within the preceding 4 hours.
(b) Water-Cooled. Conditions for an air-cooled barrel apply if coolant flow is not maintained at proper level.
(4) 3"/50 Caliber and Larger. Any gun that has fired a total of more than 50 rounds within a period of 4 hours. Applicable to the 3"/70 when cooling system is not functioning.
c. MISFIRE. A misfire occurs when, after activating the firing mechanism, a loaded gun fails to fire. This may be attributed to mechanical or electrical deficiencies or a combination of the two. These mishaps may be caused by failure of the firing pin to properly strike the primer, percussion firing, a break in the firing lead, electrical firing, a faulty primer, or some
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internal ammunition failure preventing the ignition of the propellant. In a cold gun a misfired round will not fire until the element at fault is repaired or replaced.
d. HANG-FIRE. A hang-fire is a delayed ignition of the propellant in a gun due to some imperfection in the ammunition. In a case gun there is only a remote possibility of a hang-fire of more than 20-seconds duration. In a bag type gun, however, a hang-fire has been known to last for 30 minutes. In general, the smaller the caliber the shorter the probable hang-fire interval.
e. COOK-OFF. This term is applied to the phenomena which occurs when a loaded round of ammunition is fired or detonated by heat absorbed from the walls of the surrounding gun barrel. A cook-off may occur in any of three ways:
(1) Fuze cook-off.
(2) Projectile filler cook-off.
(3) Propellant cook-off.
A cook-off can occur only in a hot gun. In general, the smaller the caliber the shorter the probable cook-off interval. Typical, but not necessarily minimum, time intervals preceding cook-offs as observed at the Naval Weapons Laboratory Dahlgren, Virginia, for various caliber weapons are:
(4) 20-mm Aircraft Guns, Time Intervals Not Available.
(a) Type I.
165 rounds continuous fire.
10 bursts of 25 rounds each, each burst separated by a 1 minute interval.
(b) Type II.
195 rounds of continuous fire.
(5) 20-mm Antiaircraft Guns.
(a) Propellant - 1.1 minutes after 480 rounds.
(b) Projectile - 1.2 minutes after 300 rounds. 3.4 minutes after 120 rounds.
(c) No cook-offs after 60 rounds.
(6) 40-mm Air-Cooled Guns.
(a) Propellant - 6 minutes after 320 rounds.
(b) Projectile - 10 minutes after 175 rounds. 18 minutes after 150 rounds.
(c) No cook-offs after 75 rounds.
(7) 40-mm Water-Cooled Guns. No cook-off has ever been known to occur in one of these barrels even after 250 rounds of continuous rapid fire, as long as the cooling system was functioning properly. Should the cooling system fail, data for the air-cooled type applies.
(8) 5"/38 Caliber Guns.
(a) Propellant - 98 minutes after 120 rounds.
(b) Projectile - 45 minutes after 154 rounds.
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(c) Projectile and Propellant - 30 minutes after 187 rounds.
(9) 3" to 8" Cartridge Case Guns.
(a) A total of 50 rounds may be fired from a cold gun at any rate of fire without danger of a cook-off. The possibility of a cook-off does exist if more than 50 rounds are fired in rapid fire or at variable rates over a 4 hour period.
(b) The 3"/70 rapid fire gun differs from the other guns of this type in that it is equipped with a barrel cooling system. As long as this system is functioning properly, the possibility of a cook-off is remote. If the cooling system fails, a hot gun will exist in the 3"/70 under the same conditions as stated in paragraph (8) (a).
f. FLARE-BACK. This term generally is applied to flaming powder gases escaping through the breech end of a gun barrel when the breech is opened. This occurs most often in bag type guns but is not solely restricted to them. It is the result of burning debris and gases from a preceding round.
3. BARREL CONDITION DETERMINATION
When failure to fire occurs, it becomes necessary to determine the condition of the barrel and ammunition in order to restore the gun to action in the safest and most effective manner. Generally this situation involves determining whether the gun is cold or hot and is governed by the definitions in paragraph 2a or 2b. Procedures for these situations are as follows:
a. COLD GUN. In a cold gun, paragraph 2a, the danger of a cook-off is nonexistent and can be neglected as a source of danger. The problem then is to determine whether a hang-fire; a misfire, or some mechanical failure is the source of trouble. In these cases proceed in accordance with the chapter of the Ordnance Publication on the specific gun involved to restore the gun to action.
b. HOT GUN. In a hot gun, paragraph 2b, failure to fire presents a much more difficult problem since the danger of a cook-off is always present. Proceed in accordance with the chapter on the specific gun involved to restore the gun to action.
4. WATER COOLING
When it is impossible to clear a live round from a hot gun within the prescribed safe time limit, see specific instructions in following chapters, the only recourse is to cool the gun immediately. Cooling the gun from the inside is considered to be the quickest and best means of reducing the temperature of the projectile and propellant. It is important to keep the barrel full of water. Too little water can be more dangerous than none, since water (steam) in small quantities acts as a better heat transfer medium than air. Water cooling from the muzzle should be used when practicable to reduce the possibility of a cook-off but it must never be considered an absolute preventive. All safety precautions should be observed and all unnecessary personnel kept clear. In the event external cooling only is used, the cooling period must be increased. In small caliber guns where internal
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cooling is not practicable, care in judging the coolness of the barrel must be exercised as the outside may be cool to the touch while the ammunition in the chamber may be near cook-off temperature. Within the safe time period, see chapter on specific gun involved, the recommended procedures for water cooling are:
a. Clear unnecessary personnel from the vicinity of the mount to avoid casualties should the projectile detonate in the bore. Those involved in cooling the gun must work quickly and keep as far from the gun as practicable.
b. Elevate the gun to some angle between 15 degrees and 30 degrees and train to safe firing bearing.
c. Fill the barrel with water and maintain a constant flow therein.
d. Spray the external surfaces of the barrel. This action is not to delay or interfere with internal cooling.
e. If breech block is partially open, flood the exposed cartridge case with water.
f. After cooling to ambient temperature, but not before 30 minutes after last attempt to fire, depress the barrel to drain the water from the bore.
g. Elevate the gun, remove the round and dispose of it in deep water if at sea, or detonate it in safe area by explosive ordnance disposal personnel if ashore.
5. GENERAL PROCEDURES
The Commanding Officer may properly prescribe the same precautions and procedures for handling the situation for noncombat practice as those recommended herein for combat, if he believes it necessary. It is often impractical to suspend operations within the danger zone around the gun for sufficient time to eliminate all danger of injury to personnel. There never can be complete assurance of safety to personnel without considerable loss of time in clearing live ammunition from a gun. The combat precautions and procedures are considered sufficiently safe to warrant their use in a noncombat condition if the loss of time might result in a serious consequence. Section 3, paragraph 26 of NAVORD INSTRUCTION 5100.1, forbids opening the breech of a gun for 30 minutes, 10 minutes for field and landing guns on shore, after the last attempt to fire. This, at the discretion of the Commanding Officer, is not obligatory in time of action. For cautions and procedures for specific guns refer to succeeding chapters.
6. GENERAL PRECAUTIONS
It should be remembered that even though a gun is hot and remains loaded, there is a safe period, see chapter on specific gun involved, in which to attempt to clear the casualty and fire the gun without danger of cook-off. Of paramount importance is the observance of safety precautions at all times. These precautions are to keep the gun trained in a safe bearing, clear all unnecessary
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personnel from the vicinity of the mount, and keep necessary personnel clear of the recoiling or moving parts. In addition, before any further attempts are made to fire, the loading mechanism must be in the firing position and any spilled propellant grains must be removed from the gun mechanism. After the gun has cooled and when not less than 30 minutes have elapsed since last attempt to fire, the gun may be unloaded. If a clearing charge is used, the gun must be depressed and all water drained from the bore before firing. In peace time prior to firing an extended practice, it is recommended that fire hoses with pressure up to the nozzle valve be readily available for external and internal
cooling of a hot gun barrel. A fog applicator with fog nozzle removed is recommended as the best means of applying water to the bore for internal cooling.
7. EXCEPTION
The instructions in this publication apply only in situations in which it is either impossible or unsafe to remove the round of ammunition by normal firing of the gun. Specifically, they do not apply where the round remains in the gun as a result of a normally executed cease-fire order. In such cases, the gun should be fired on command of the officer in charge of the exercise.
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Chapter 3 PROCEDURES FOR CALIBER .50 MACHINE GUN
1. GENERAL DATA
Tests have been conducted to determine the number of rounds which can be fired in the caliber . 50 gun without causing a cook-off. It has been determined that 150 rounds can be fired from an aircraft barrel and 300 from an antiaircraft barrel without reaching cook-off conditions. Exceeding the number of rounds stated above will result in a hot gun condition. Cook-offs in this gun generally consist of igniting the propellant causing the round to be fired in a normal manner. There is danger from the emerging projectile but no damage to the gun is expected if the breech is closed. Cook-offs usually occur between ten seconds and five minutes after the round is loaded. Therefore, it is essential that a live round, left in a hot gun, be removed immediately, within 10 seconds. An alternative procedure is to allow the round to remain in the gun until the barrel has cooled to ambient temperature.
2. GENERAL PROCEDURES
The following procedure is recommended:
a. Train and elevate the gun to a safe line of fire.
b. Clear all unnecessary personnel from the vicinity of the
mount.
3. NONCOMBAT PROCEDURES
a. COLD GUN.
(1) Breech Not Closed. Open the breech and back out the round.
(2) Breech Closed. Twenty seconds after last attempt to fire, open breech, back out the round and dispose of it.
b. HOT GUN.
(1) Breech Not Closed. Open breech immediately, remove round and dispose of it. If breech is jammed partly open, apply water cooling immediately, chapter 2, paragraph 4.
(3) When gun barrel has been cooled to ambient temperature, but not before 30 minutes after last attempt to fire, open the breech, remove the round and dispose of it.
4. COMBAT PROCEDURES
a. COLD GUN.
(1) Breech Not Closed. Open breech and back out the round.
(2) Breech Closed. Twenty seconds after last attempt to fire, open breech, back out the round and dispose of it.
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b. HOT GUN.
(1) Breech Not Closed. Open breech immediately remove round and dispose of it. If breech is jammed, apply water cooling
immediately, chapter 2, paragraph 4.
(2) Breech Closed. Apply water cooling immediately, chapter 2, paragraph 4, open breech and remove round as soon as barrel has reached ambient temperature.
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Chapter 4 PROCEDURES FOR 20-mm GUNS
1. GENERAL DATA
A projectile lodged in the bore of a 20-mm barrel can more readily be removed by using the special backing out tools provided for this purpose than by loading short cartridges. Therefore, short cartridges are not provided for these guns. The procedures outlined in this chapter require no tools other than those supplied with the gun, with the exception of a safety handle on the backing out rod. The safest time to remove live ammunition from a hot 20-mm barrel under emergency conditions is between 5 and 60 seconds after the stoppage occurs. No 20-mm hang-fire is known to have lasted more than a fraction of a second. The danger of a cook-off continues even after a round has been unloaded from the gun. Instances have been reported wherein an unloaded round exploded while in the air after being thrown overboard. In the interest of safety, it is emphasized that every effort must be made to unload a hot gun in the shortest possible time. All other safety precautions contained in the applicable gun publications should be observed. In the event a live round remains in the chamber of any 20-mm barrel that has been heated to a high temperature, cook-off will occur approximately 60 seconds after misfire.
2. AIRCRAFT GUNS
Aircraft gun mechanisms are of two types.
Type 1. 20-mm Mechanisms M1, M2, and M3 are designed so that the
cycle is completed when the breech block of the gun is in the rear or open position. Unless some malfunction of the mechanisms or ammunition occurs, no round will be left in the chamber at the end of any firing cycle. Tests conducted on these guns have shown that temperatures of approximately 170°C in these barrels will cause a cook-off of the round. This temperature will be reached after either firing 10 bursts of 25 rounds, each burst separated by a 1 minute cooling interval, or a continuous burst of 165 rounds.
Type 2. 20-mm Mechanism Mk 12 is designed so that the breech block is closed on a live round of ammunition in the gun chamber on the completion of an action cycle. In this gun a temperature of 195° C will cause a cook-off of the round. Such a temperature can be expected after approximately a 195-round burst. The following procedures apply to aircraft guns fired at proving activities and do not apply to guns in aircraft.
a. Elevate and train the gun to a safe line of fire.
b. Clear all unnecessary personnel from the vicinity of the mount.
c. Cold Gun.
(1) If the gun is a Mk 12, make a second attempt to fire.
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(2) After 30 minutes extract round and resume firing.
d. Hot Gun.
(1) If the gun is a Mk 12, make a second attempt to fire.
(2) Wait 30 seconds, extract round and dispose of it immediately.
(3) If round cannot be extracted within 30 seconds, introduce water into the muzzle of the gun, chapter 2, paragraph 4, and begin external spraying of the barrel.
(4) After gun has cooled to ambient temperature, but not before 30 minutes after last attempt to fire, remove the round and dispose of it.
3. ANTIAIRCRAFT GUNS
(20-mm Mk 2 and Mk 4) In the event of a misfire in 20-mm gun Mk 2 and 4, it is impracticable to attempt to fire the round a second time. The only recourse is to clear the gun. A hot gun condition will exist in these guns after a 115-round burst. In removing any ammunition components from a hot gun, a glove should be worn as protection against the heat. Ammunition removal should be accomplished with any convenient tool such as a screwdriver. Under no circumstances are the bare hands to be used for this purpose as serious finger injuries have resulted from the unexpected closure of the breech blocks. The following procedures are recommended.
a. GENERAL PROCEDURES.
(1) Elevate and train the gun to a safe line of fire.
(2) Clear all unnecessary personnel from the vicinity of the gun.
(3) Insure that the safe fire lever is in the safe position.
b. NONCOMBAT PROCEDURES.
(1) Cold Gun.
(a) Wait 30 seconds, remove the magazine observing necessary safety precautions for a magazine jam, and remove the round.
(2) Hot Gun.
(a) Remove magazine immediately observing necessary safety precautions for magazine jam, and remove round.
(b) In the event the round cannot be removed within the 60-second period, apply water cooling.
(c) If recoiling parts are in the fully forward position, apply water cooling immediately.
(d) When gun has been cooled to ambient temperature, but not within 30 minutes of last attempt to fire, remove round and dispose of it.
c. COMBAT PROCEDURES.
(1) Cold Gun.
(a) Remove magazine immediately observing precautions for magazine jam, and remove round.
(2) Hot Gun.
(a) Remove magazine immediately observing precautions for magazine jam, and remove round.
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(b) If round cannot be removed, remove the barrel keeping it pointed in a safe direction, and immerse it in water or dispose of it
over the side. This action must be accomplished within 60 seconds of the time of misfire.
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Chapter 5 PROCEDURES FOR 40-mm GUNS
1. GENERAL DATA
Projectiles lodged in the bores of 40-mm gun barrels can be removed more readily by using the special backing out tools provided for this purpose than by loading short cases. Therefore, short cases are not provided for these guns. No other tools are required to accomplish the procedures outlined in this chapter other than those supplied with the gun. When more than 75 rounds have been fired from an air-cooled barrel, within the preceding 4 hours, it shall be considered a hot gun. If a misfire occurs in an air-cooled gun, there is a safe period of 5 minutes during which the gun can be cleared by firing or backing out the round without cooling. A waiting period of 30 seconds is required after the last attempt to fire before unloading. Following a misfire in either air-cooled or water cooled guns, recocking and firing may be accomplished instead of extracting case. This procedure should not be attempted more than once.
WARNING
Recocking these guns is somewhat dangerous since it involves unlocking the breech block so that a hang fire or cook-off might blow the breech open. Tests have shown that approximately 25 percent of the misfired cases have fired on the second attempt, but rounds which had misfired twice could very seldom be fired by additional attempts. Additional efforts to fire shortens the
time available for extraction prior to a cook-off. In the event extraction is attempted and the round separates, the ejector tool should be inserted through the muzzle to clear the bore. Time permitting, the bore should be examined for the presence of TNT which may have melted and exuded from the projectile. TNT will appear as a crystalline substance and should be removed by scraping with a copper, brass, or bronze tool. The bore then should be wiped with a clean cloth. Procedures for clearing live ammunition from the water-cooled barrel are the same as for the air-cooled barrel, if water cooling has failed. When the coolant flow in the water cooled barrel is maintained under normal pressure, the possibility of cook-off does not exist. Should the cooling system fail, procedure for the, air-cooled gun will apply.
2. GENERAL PROCEDURES WHEN MISFIRES OCCUR
a. Train and elevate the gun to a safe line of fire.
b. Shut down train and elevating power drives.
c. Remove all live fuzed rounds from the vicinity of the mount.
d. Clear all unnecessary personnel from the vicinity of the
mount.
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3. NONCOMBAT PROCEDURES
a. COLD GUN.
(1) Wait 30 seconds. Open the breech and remove the round.
b. HOT GUN.
(1) If breech block is not fully closed, open the breech immediately and discard round as no hang-fire could occur.
(2) If breech is closed, wait 30 seconds. Open breech, remove and discard round.
(3) If round cannot be removed in the 5-minute safe period, proceed with water cooling, chapter 2, paragraph 4.
(4) If gun has a water-cooled barrel, attempt to restore coolant flow.
(5) When gun has been cooled to ambient temperature, but not before 30 minutes after last attempt to fire, open the breech and remove the round.
4. COMBAT PROCEDURES
a. COLD GUN.
(1) Wait 10 seconds, open the breech and remove the round.
b. HOT GUN.
(1) If breech block is not fully closed, open the breech immediately; remove and discard the round.
(2) If breech is fully closed, make a second attempt to fire the gun. This can be accomplished in the following manner.
(a) Rotate the hand operating lever about 50° from its secure position until the rammer cocking lever engages the rammer shoe. This position can be determined easily because of the increased force necessary to move the lever beyond this point.
(b) Return the lever to its secured position and fire the gun.
(3) If round does not fire, wait 10 seconds. Then remove the round and dispose of it.
(4) If round cannot be removed in the safe 5-minute period, proceed with water cooling, chapter 2, paragraph 4.
(5) For a water-cooled barrel in which cooling has failed, follow the same procedure, but attempt concurrent action to restore coolant flow.
(6) When barrel has been cooled to ambient temperature, open breech and remove round.
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Chapter 6 PROCEDURES FOR CASE TYPE GUNS (3" - 5" - 6'' - 8")
1. GENERAL DATA
When guns of these calibers have been fired more than 50 rounds within a 4-hour period at any rate of fire, they are considered to be a hot gun. This condition is not true of the 3"/70 unless the cooling system fails. There is no danger of a hot gun condition in the 3"/70 rapid fire gun as long as its barrel cooling system functions properly. Once these barrels have been heated to cook-off temperatures, they can be maintained at such temperatures under the following firing programs:
a. 3"/50 - 30 rounds per hour
b. 3"/70 - 30 rounds per hour if cooling system fails
c. 5"/38 - 15 rounds per hour
d. 5"/54 - 12 rounds per hour
e. 6"/47 and 8"/55 - 10 rounds per hour
In the event of failures to fire after above guns have reached their cook-off temperature there is a safe period of 10 minutes after loading during which the conditions causing the failure may be corrected. The hotter the gun, the greater the urgency for corrective action.
2. CLEARING CHARGES
When an unfired round is removed from a gun, there is a possibility that the projectile will be left
in the bore. In the case of semi-fixed ammunition, it is certain that the projectile will be left. When this occurs, the best way to remove the projectile is to fire it out the muzzle. For this purpose short cartridge cases, known as clearing charges, are provided.
a. ALLOWANCES. Allowances for these charges have been established as follows:
(1) Guns Aboard Combat Ships. One per gun, plus one per mount, three for each twin mount aboard ship.
(2) Guns Aboard Auxiliary Ships. One per gun, plus a total of one reserve aboard ship.
(3) Guns Mounted Ashore. Two per mount except for training centers which are allowed five per mount.
b. PROCEDURES.
(1) Fixed Ammunition - 3"/50, 3"/70, 5"/25. Short cartridges for these guns should be loaded into the gun by hand after clearing the chamber of any loose material and then seated by hand or power ramming as practicable.
(2) Semi-Fixed Ammunition 5"/38, 5"/54, 6"/47, 8"/55. When these cases are extracted, they may be replaced with a new cartridge of standard, or short length. The size depends on the haste required or
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presence of foreign material, such as cork or plastic, in the chamber. In loading the 5"/54 and 6"/47 cartridges, it is recommended that they be inserted by hand and then seated by hand or power ramming as desired. The 5"/38 and 8"/55 short cartridges have a combination primer and must be inserted by hand, using manual operation for closing the breech. A portable percussion firing device can be attached to fire the short cartridges, if electrical firing circuits fail. Short cartridges for these guns are shorter than their standard cases by considerable amounts, compared to those for fixed ammunition. This reduces the difficulty in loading behind a partially seated projectile.
3. GENERAL PROCEDURES
In the event of a failure to fire, the following procedure is recommended:
a. Train and elevate the mount to a safe line of fire.
b. Shut down the ammunition power drive.
c. Clear all unnecessary personnel from the vicinity of the gun.
d. Determine whether the breech block is opened or closed.
4. NONCOMBAT PROCEDURES
a. COLD GUN.
(1) Breech Block Is Not Fully Closed.
(a) Attempt to close block by power or manual operations.
(b) If breech block will not close, open the breech and extract the round.
(c) If the round is only partly extracted, projectile remains seated:
1. Examine the chamber and insure that all powder grains have been removed.
2. Load another case, short case if necessary, and close the breech block.
3. Insure that mechanisms and obstructions are clear of the recoiling parts and that the empty case tray, deflector, is in position as appropriate, and fire the gun.
(2) Breech Block Is Fully Closed - Gun Fails To Fire.
(a) Wait 30 seconds and attempt to fire the second time with normal firing circuits. If gun fails to fire, attempt to fire using auxiliary firing circuits.
(b) Wait 30 minutes after last attempt to fire, open the breech, remove the round and dispose of it in deep water if at sea, or detonate it in a safe area by explosive ordnance disposal personnel if ashore.
(c) If round is only partly extracted, projectile remains seated, follow procedure (1) (c).
b. HOT GUN. In a hot gun the possibility of cook-off of the propellant or projectile is always present. The ammunition, in this case must be cleared from the gun within the allowable safe ten minute period
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after the misfire has occurred, or the barrel must be cooled to ambient temperature.
(1) Breech Block Is Not Fully Closed.
(a) Attempt to close block by manual or power operation.
(b) If breech block does not close, open the breech within the safe 10-minute period. Then remove the round and dispose of it in deep water if at sea, or detonate it in a safe area by explosive ordnance disposal personnel if ashore.
(c) If round is only partly extracted, projectile remains seated:
1. Examine the chamber and insure that all powder grains have been removed.
2. Load another case, short case if necessary, and close breech block.
3. Insure that mechanisms and obstructions are clear of the recoiling parts and that the empty case tray, deflector, is in position as appropriate and fire the gun.
(d) If firing is not successful, proceed with water cooling at once in accordance with chapter 2, paragraph 4.
(2) Breech Block Is Fully Closed - Gun Fails To Fire.
(a) Make further attempts to fire the gun immediately using auxiliary firing circuits if normal firing circuits fail.
(b) If gun fails to fire within 2 minutes of initial attempt to fire, cease further attempts to fire and proceed with water cooling at once in accordance with chapter 2, paragraph 4.
(c) If gun is a 3"/70, commence concurrent efforts to restore coolant flow through its cooling system.
5. COMBAT PROCEDURES
The procedures for clearing live ammunition from the gun may be based upon a minimum delay procedure at the discretion of the Commanding Officer. Should a misfire occur, recommended procedure is as follows:
a. COLD GUN
(1) If the breech is not fully closed, open the breech and extract the round. When assured of satisfactory mount operation, reload and continue firing.
(2) If the round is only partly extracted, projectile remains seated:
(a) Examine the chamber and insure that all powder grains have been removed.
(b) Load another case, short case if necessary, and close the breech block.
(c) Insure that mechanisms and obstructions are clear of the recoiling parts and that the empty case tray, deflector, is in position as appropriate and fire the gun.
b. HOT GUN. Follow the same procedure as for cold gun except:
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(1) If a case has been loaded but cannot be fired, begin water cooling the barrel immediately in accordance with chapter 2, paragraph 4.
6. GENERAL PRECAUTION
Whenever a loaded case is extracted from a gun, powder may be
spilled. This is particularly true with semifixed ammunition. The loose powder grains in a hot gun can ignite and set off the explosive elements of the round. In either a hot or cold gun it can lead to jamming in the weapon. Care should be exercised to remove all such debris before loading any gun after a misfire.
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Chapter 7 PROCEDURES FOR BAG TYPE GUNS (8" AND 16")
1. GENERAL DATA
In bag type guns the heat input to the barrel is of such a low order that the danger of a cook-off is remote. However, such a condition could occur if shore bombardment or an engagement of prolonged duration were encountered. Misfires and hang-fires however, can occur and in the case of hang-fires have been known to endure for 30 minutes before firing. There have been cases in which the powder bags have been placed in the gun chamber with their ignition ends towards the muzzle. When this happens, a misfire or hang-fire can occur. It has been determined that such charges can be ignited by firing a series of primers into it. Elevation of the gun to maximum elevation and rocking it in the trunnions may aid in sliding the charge to a firm seat on the mushroom face.
2. GENERAL PROCEDURES
A recommended procedure is as follows when a hang-fire or misfire occurs:
a. Elevate and train the mount to a safe line of fire.
b. Clear all unnecessary personnel from the vicinity of the gun.
c. The crew shall never leave a loaded gun until the directions of the following paragraphs have been complied with.
3. NONCOMBAT PROCEDURES
a. COLD GUN.
(1) Keep the breech mechanism fully closed.
(2) Exercise care to avoid danger from recoil or flareback.
(3) Continue attempts to fire. Do not leave the firing lock open any longer than necessary when changing primers.
(4) If the gun fails to fire proceed as follows:
(a) Open the firing key and break the firing circuit elsewhere.
(b) Unhook the firing lanyard if detachable.
(c) Remove the primer from the firing lock with the primer tools supplied for this purpose provided such action will not open the breech.
(d) One hour after last attempt to fire, open the breech, remove powder and dispose of it over the side or immerse in water.
b. HOT GUN.
(1) Follow the procedure outlined for a cold gun except for paragraph (3) (a) (4) (d).
(2) The 1-hour wait is not obligatory if in the opinion of the
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Commanding Officer there is danger of a projectile cook-off.
4. COMBAT PROCEDURES
Follow the noncombat procedures
except that the 1-hour waiting period is not obligatory if in the opinion of the Commanding Officer the procedure would jeopardize the ship in action br that there would be danger of a projectile cook-off.
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DISTRIBUTION
SNDL Part 1 (No. 72) and Part 2 (No. 29)
One copy to each unless otherwise indicated:
Requests for additional copies of NAVWEPS OP 1591 (First Revision) should be submitted on S&A Form 1093 to the appropriate Forms and Publications Supply Point.
