12. Maintenance, testing, and repair of Pistols Mk 6 and Mk 6 Mod 1, as noted in this pamphlet, is generally applicable to Pistol Mk 6 Mod 2. The following supplementary infor-mation and instructions should be observed in this connection:

(a) The construction of the Pistol Mk 6 Mod 2 is intended to be such as to withstand ex-posure to weather conditions on decks of ships for a period of three months without harmful effect to the internal operating parts. Therefore, the "Monthly Inspect-ion Test" by Secondary Stations as noted in NAVORD OCL M7-44 for Pistols Mk 6 and Mk 6 Mod 1 is not required for Pistol Mk 6 Mod 2. However, if the three-month ser-vice period is not realized and the condition of any pistol indicates that inspections and test should be per-formed, such material should be turned in to a "Secondary" or "Main Station" for suitable action.

(b) Forces afloat should turn in, quarterly or as soon thereafter as practicable, Pistol Mk 6 Mod 2 to a convenient "Main Station" as defined in NAVORD OCL M7-44 for a "Quarterly Inspection Test."

(c) A torque wrench, Figure 5, will be supplied by the Bureau of Ordnance. This wrench is required by "Main and Overhaul Station" as defined in NAVORD OCL M7-44, to screw the depth setting mechanism for deep firing into place as noted on figure 4. The torque h applied to assemble the mechanism should be not less than 40 60 ft./lbs. nor more than 50 75 ft./lbs. It is intended that the torque applied within the limits noted should produce the desired result of watertightness with a minimum elongation of the mechanism body. The torque wrench should be used with wrench, figure 6, for assembling the deep firing mechanism. The latter wrench is simple and can be fabricated locally by the respective activities.

(d) The air pressure required for Depth Charge Test Set Mk 3 to test and calibrate sub-assemblies of Pistol Mk 6 Mod 2 should be increased from 300 to 375 psi. Three pressure gauges, each with a range of 0-600 psi, will be furnished by the Bureau of Ordnance to provide for this change. One each of these gauges should be used to record the test set air tank pressure and to record the pressure at the calibrating and/or leakage testing fixture. The third gauge should be used for a periodical check of the accuracy of the working gauges when a gauge tester is not available. When a test program is underway, the gauges should be checked at least twice weekly and oftener if necessary. The work-ing gauges should he maintained at an accuracy of plus or minus two psi within the range of 100 to 350 psi. Pressure application for test and calibration of Pistol Mk 6 Mod 2 and its subassemblies should be controlled so that the gauge pressure rises at the rate of approximately 11.0 psi per second.

(e) The standard deep firing functional test for completely assembled Pistol Mk 6 Mod 2, using pistol testing fixture of Depth Charge Test Set Mk 3, should not be performed at a depth setting of greater than 600 feet. The watertightness feature and construction of the pistol testing fixture make it unsafe for pressures greater than that equivalent to the 600-foot depth setting.

(f) The blade on the screwdriver attachment of the Test Set Mk 3 calibrating fixture should be modified to suit the construction of the deep firing mechanism as shown on figure 3. This is a simple operation and it can readily be performed by activities operating Test Set Mk 3.

(g) When pistol firing plungers are overhauled by a "Secondary" or "Main" station as no-ted in NAVORD OTI M2-44, burred release plungers should be replaced. Steel release plungers from spare parts should be used for replacement. These may be readily identi-fied by their parkerized (black) finish. Burred release plungers may cause incomplete cocking of the pistol, which would result in accidental firing of the detonator.

(h) The disassembly of the deep firing mechanism, figure 3, of Pistol Mk 6 Mod 2 is per-formed as follows:

(1) Submerge assembly in water up to a point just below the end surface of the spring adjusting screw and use a small torch to melt the solder which locks the spring retainer nut. Remove this nut. Then melt the solder which locks the spring adjusting screw and remove the screw. The assembly is submerged in water dur-ing this operation to dissipate heat, which would have a harmful effect on the gland seal and spring. Both the spring retainer nut and the spring adjusting screw should be re-moved while the solder is in the molten state.

(2) Remove the spring and spring retainer and valve piston with attached ball valve.

(3) Remaining parts of the assembly are similar to the corresponding parts of the Pistol Mk 6 Mod 1 and should be handled as noted in this pamphlet.

(i) Bellows replacement must be made with new type thin wall (0.005 in.) thickness bel-lows. This bellows will be suitably marked for identification when supplied by the Bureau of Ordnance to "Overhaul" stations which are defined in NAVORD OCL M7-44.

(j) Stem, piston, and key subassembly, figure 7, must be used for replacement whenever it is necessary to replace this subassembly during overhaul.

(k) Spring engaging collar, figure 8, must be used for replacement, if such is found to be necessary during quarterly inspection or overhaul.

(l) Dial plate, figure 9, must be used for replacement if such is found to be necessary during quarterly inspection or overhaul.

(m) Plastic gasket, figure 10, must be used for replacement whenever subassembly, figure 4, is broken down.

(n) Assemble the deep firing mechanism, figure 3, as follows:

(1) Screw valve seat (432902) in place against shoulder in housing (432903).

(2) Put dial plate (433981) in place with stop against indicator point on valve seat (432902). Then rotate both dial plate and valve seat clockwise to match holes in dial plate with nearest holes in housing. Insert dial plate locating pin (421099). This pin must be pressed into place and the end of the pin must be flush with the top surface of the dial plate. Remove the dial plate.

(3) Insert gland seal (421093). Use a new gland seal which has been immersed for approximately one hour in raw castor oil (421146).

(4) Screw packing nut (421092) down on gland seal. Packing nut must be screwed down flush with top surface of housing or slightly below it.

(5) Attach dial plate with four self-tapping screws (421094).

(6) Insert piston and ball valve (421069).

(7) Insert spring retainer (421109) and spring (421132).

(8) Assemble spring adjusting screw (421110) and screw it down until it lightly con-tacts the shoulder on the spring retainer.

(9) With a small chisel, lightly stake the internal thread of the housing adjacent to -one end of the screwdriver slot in the spring adjusting screw. This is done to produ-ce a slight tightness of fit, so that the spring adjusting screw will retain its adjusted lateral position when so placed during the subsequent calibrating operation. The me-chanism is now ready for calibration.

(o) Calibrate the deep firing mechanism, figure 3, of the Pistol Mk 6 Mod 2 in the calibrat-ing fixture of Depth Charge Test Set Mk 3 as follows:

(1) Set the pointer to the 700-foot mark and place the mechanism in the calibrating fixture.

(2) Apply water pressure with control valve "C," as shown on diagrams furnished with test set. Allow pressure to increase at the rate of approximately 11 psi per second until the valve opens wide. This can be determined by a sudden rush of water, as compared with a slight trickle which occurs at a few pounds before the actual opening point. The opening pressure should be observed. Then the pressure should be reduced until the valve closes. Complete closing of the valve will be insured by reducing the pressure 50 psi below the point where most of the water flow suddenly ceases.

(3) The valve should open within the range 290 to 315 psi. The valve spring tension should be controlled by turning the adjusting screw to bring the valve opening pres-sure within the range noted,- while repeating the cycle of pressure application and release.

(4) When the opening pressure within the required range has been obtained, two cycles of pressure application and release should be made without disturbing the po-sition of the adjusting screw. These two valve operating cycles should be made to check the satisfactory opening pressure initially obtained.

(5) On the second valve operating cycle, inspection for leakage at a pressure of 170 psi should be made. In this connection, an amount of leakage not in excess of 10 cu. in. (164 cc) in one minute is considered satisfactory. Leakage greater than this amount is cause for rebuilding the mechanism. The required pressure noted for leak-age inspection should be attained by increasing the pressure from 140 psi.

(6) Chattering or vibrating of the valve at a point of opening within the required range as noted indicates an unsatisfactory mechanism. This condition is generally caused by defective parts. Precautions should be taken to see that all test appara-tus valves in the direct waterline to the test fixture are open wide during this test, because pipe line restrictions may cause valve chattering or vibration.

(p) After the deep firing mechanism has been satisfactorily calibrated to function within the required limits, it should be carefully removed from the calibration fixture in order not to disturb the position of the spring adjusting screw. As soon as practicable, the adjust-ing screw should be locked in place by soldering - see Note 7, figure 3, to prevent any possibility of change in calibration.

(q) After the spring adjusting screw has been locked in place with solder, the index poin-ter of the depth setting mechanism should be registered to the column of the letter "T" in the word "FEET" engraved on the dial plate-see figure 3. Retainer nut (421130) should be screwed down on spring retainer (421109) until it is finger tight against the spring ad-justing screw (421110). Precautions must be taken to see that the contact surface bet-ween the spring adjusting screw and retainer nut is clean and free of any foreign sub-stance. The retainer nut should be locked to the spring retainer by use of a small torch and fine wire solder. This operation should be performed with the mechanism immersed in water as noted in figure 3 and with due care to avoid solder getting into the hole in the spring retainer stem or holes and slots in spring adjusting screw.

(r) Remove dial plate and apply shellac (421143) to surface of housing and put gasket (421091) in place. Apply shellac to top surface of gasket and replace dial plate and se-cure it with four self-tapping screws (421094).

(s) Upon completion of the operations of locking the spring adjusting screw and the spring retaining nut of the deep firing mechanism with solder, the mechanism should be blown out with air. Set the point against the stop at the 0 - to - 300 position and insert the nozzle of the air hose in the hole on the valve seat for the blowing-out operation.

(t) The depth setting mechanism for deep firing should be assembled with associated parts as shown in figure 4 for a recheck on operation and a test of watertightness in the leakage test fixture of Depth Charge Test Set Mk 3. Torque wrench described in para-graph 12(c) should be used to screw deep firing mechanism into place. The subassembly should comply with the following requirements in order to be considered satisfactory for use:

(1) With the depth setting pointer registered at the 400 mark, the valve opening pressure should be within the range of 150 to 180 psi. Pressure should be applied at the rate of approximately 11.0 psi per second. While the pressure is rising from 0 to valve opening pressure, an examination should be made for leakage through the dial plate gasket or through the, valve. Leakage not in excess of ten cubic inches (164 cc) in one minute is satisfactory.

(2) The valve closing pressure should be within 46 to 90 psi of the pressure at which the valve opened. This closing pressure should be obtained after the valve opens, by a gradual reduction of the applied pressure until the valve snaps closed.

(u) After subassembly, figure 4, has been subjected to recheck and watertightness test, the depth setting pointer should be set against its stop at 0 - to - 300 and the complete subassembly dried off by blowing with an air hose. Then the subassembly should be dip-ped in rust preventive compound (421147). Following this operation surplus compound should be drained off and the valve blown out as follows:

(1) Place the nozzle (421425) of the air hose in the hole in the valve seat and apply approximately 150 psi air pressure until traces of rust preventive compound can no longer be noted in the air stream which issues from the open end of the depth set-ting sleeve. Also blow out any traces of rust preventive compound which remain in the cavity surrounding the head of the valve seat.

(2) With respect to the application of rust preventive compound in general, it is im-portant that excessive deposits of compound do not collect around packing glands, in water inlet openings or on parts working with close clearances, such as balls. If these undesirable conditions are allowed to exist, restricted water openings, locked valves, and deteriorated gaskets will result. After treatment with rust preventive compound, subassemblies and parts must be allowed to dry to permit complete eva-poration of the compound vehicle. This drying may be accelerated by passing the parts and subassemblies through a steam or hot air type drier at a temperature of 200o F for approximately two minutes. If such driers are used, means should be pro-vided to remove the vapor.

13. Booster Extender Mechanism Mk 6 Mod 2, figure 2, is basically the same as Ex-tender Mechanism Mk 6 Mod 1. However, several minor changes in operation have been introduced to meet the functional requirements imposed by the expanded depth setting range of the Pistol Mk 6Mod 2. This mechanism may be used in Depth Charge. Cases Mk 9 Mods 2 and 3 with Pistols Mk 6 and Mk 6 Mod 1. In this connection, it should be noted that Booster Extender Mechanism Mk 6 Mod 2 must be used with Depth Charge Pistol Mk 6 Mod 2. Other booster extender mechanisms now in service are not suitable for use with this pistol.

14. New and redesigned appendages as follows are attached to the Depth Charge Booster Extender Mk 6 Mod 2:

(a) The bellows (421174) installed in Extender Mechanism Mk 6 Mod 2 is made of 0.012-inch thickness material. The use of such material is required to withstand pressure of equivalent to 1000 feet depth.

(b) Spindle (421172). spindle guide (421171). locking slide (421170), and balls (421157), as shown on figure 11, function to limit the extension of the mechanism in the following manner, so that the booster can will not be forced against the centering flange at the end of the pistol when the can has been moved into the armed position by extension of the bellows, under the influence of hydrostatic pressure:

(1) As water enters the chamber it extends the bellows and forces the piston and spindle inward. Since the locking slide is locked to the spindle by the locking balls, the slide is carried inward with the spindle against the resistance of the extender spring. When the spindle moves far enough inward to carry the locking balls into the enlarged bore of the spindle guide, the balls slip outward into the guide a distance sufficient to permit further independent inward movement of the spindle until the shoulder at the large diameter of the spindle contacts the balls. The spindle is then stopped at the end of its travel because the balls are attached to the slide, which is held by its shoulder bearing against the inner end of the guide.

(2) The space between the top of the booster can and the adjacent surface of the pistol centering flange when the booster is in the armed position, is approximately 1/10 inch.

(c) A soft copper gasket (421179) is inserted between the spindle shoulder and the boss on piston (421173) to maintain a watertight seal at this joint. Additional precautions are taken for sealing at this point by the application of plastic lead seal joint and thread compound to the screw threads of the mating parts. This joint is sweated with solder on Extender Mechanisms Mk 6 and Mk 6 Mod 1.

(d) Plain and knobbed safety forks furnished with the extender mechanism are des-cribed in NAVORD OTI M12-43.

15. Installation of booster extender mechanism in a depth charge case should, in general, be in accordance with instructions noted on page 91 of this pamphlet. However, the following supplementary instructions should be noted in this connection:

(a) The extender mechanism with attached booster should be installed in a depth charge case before the pistol with its attached detonator is assembled in place.

(b) When changing safety forks on depth charges in release tracks, it will be found that considerable effort is required to pull the spindle out after the plain type safety fork has been removed. This is due to the higher spring rate of the new heavy wall bellows as compared with the bellows used in Extender Mechanism Mk 6 and Mk 6 Mod 1 The cha-racteristic noted in this instruction will also be encountered when performing daily routine on extender mechanisms. Therefore, personnel detailed to work on depth charges should take security precautions when performing these operations on the aftermost depth charges in release tracks, which on some ships overhang the stern on the outboard side.

16. Extender mechanism upkeep routine for ships in accordance with this pamphlet should be carried out.

17. Maintenance testing and repair of Extender Mechanisms Mk 6 and Mk 6 Mod 1, as noted in chapter VI, is generally applicable to Extender Mechanism Mk 6 Mod 2. The fol-lowing supplementary information and instruction should be observed in this connection:

(a) The construction of the Extender Mechanism Mk 6 Mod 2 is intended to be such as to withstand exposure to weather conditions on decks of ships for a period of three months without harmful effect to the internal operating parts. Therefore, the "Monthly Inspection Test" by "Secondary" stations as noted in NAVORD OCL M7-44 for Extender Mechanisms Mk 6 and Mk 6 Mod 1 is not required for Extender Mechanism Mk 6 Mod 2. However, if the three-month service period is not realized and the condition of any extender mecha-nism indicates that inspection and tests should be performed, such material should be turned in to a "Secondary" or "Main" station for suitable action.

(b) Forces afloat should turn in, quarterly, or as soon thereafter as practicable, Extender Mechanism Mk 6 Mod 2, to a convenient "Main Station" as defined in NAVORD OCL M7-44 for a "quarterly Inspection Test."

(c) The standard functional test procedure for Booster Extender Mechanism Mk 6 Mod 2 is the same as that noted in this pamphlet for Extender Mechanisms Mk 6 and Mk 6 Mod 1, except that the full travel permitted by the extender test stop should occur at a pres-sure of 4 to 11 psi to be satisfactory.

(d) Disassembly of the Extender Mechanism Mk 6 Mod 2 for overhaul is accomplished as follows - figure 12 should be used in this connection:

(1) Unscrew and remove bellows guard (432905), using the strap wrench. Unscrew booster connecting collar (421155) and remove bellows retainer (433050).

(2) Unscrew and remove packing gland (421165).

(3) Remove three screws (421161) securing spindle hushing.

(4) Insert a suitable rod through the hole in the outer end of the spindle and un-screw the spindle from the piston.

(5) With the rod still in place through the spindle, withdraw the subassembly, figure 11, from the carrying flange.

(6) Unscrew spindle guide (421171) and remove the remaining parts of the subas-sembly.

(7) The subassembly, figure 13, may be tested for leaks as noted in the instructions of the enclosure.

(e) Assembly of the Extender Mechanism Mk 6 Mod 2 is accomplished as follows - figure 12 should be used in this connection:

(1) Make up subassembly as shown in figure 14.

(2) Then, as shown in figure 11, insert locking slide (421170) and spring (421156); screw spindle guide (421171) into place and stake it.

(3) Now, with subassembly held with the spindle guide uppermost, insert spindle (421172) through spindle bushing and push it upward until the end is slightly below the locking ball holes in the slide.

(4) Drop three locking balls (421157) into the bore of the locking slide. These balls will rest on the end of the spindle, and they can be worked into the respective holes by appropriate movement of the subassembly.

(5) After the balls are located in the holes, push the spindle upward. The shoulder at the base of the thread on the end of the spindle will contact the balls projecting from the slide, and the slide will be carried upward, with the spindle and against the resistance of the spring, until the balls recede into the enlarged bore of the spindle guide. Push the spindle further upward. When the spindle ball recess comes in line with the balls in the spring loaded slide, the balls will be forced into the spindle re-cess and the slide and spindle will be locked together. Release the upward thrust on the spindle. All parts will now be properly combined to form the subassembly.

(6) Place soft copper gasket (421179) on the piston boss of subassembly, figure 13, and place 0.010-inch thickness hydroil gasket (421164) in the spindle bushing recess of the carrying flange.

(7) Coat threads on end of spindle with plastic lead seal joint and thread compound (421145) and insert subassembly, figure 11, into subassembly, figure 13. With a rod inserted through the hole in the outer end of the spindle screw the spindle into the piston. This threaded joint should be made tight, but excessive torque should not be used because of danger of stripping the thread or twisting off the spindle at the thread relief. About 10 ft./lbs. of torque should be applied.

(8) Secure spindle bushing with three screws (421161) and stake these screws to lock them in place.

(9) Check one out of ten units thus assembled in accordance with note (1) of figure 12.

(10) Place bellows retainer (433050) in position, screw booster connecting collar (421155) on end of spindle and lock it by staking.

(11) Attach bellows guard (432905) and lock it by staking as shown in figure 12.

(12) Make up gland seal (421166) and gland (421165). Gland seals should be immer-sed in raw castor oil (421146) for approximately one hour before using.

(13) Attach plain safety fork (421152), and test operation of spindle locking gear in accordance with note (4) in figure 2.

(14) One percent of overhauled Extender Mechanisms Mk 6 Mod 2 should be tested in accordance with paragraph 21(n), pages 168 and 169 of this pamphlet, except that the limit of travel of extender piston and applied water pressure shall be 1.90 inches and 375 psi respectively.

18. Maintenance procedure for Pistol and Extender Mechanism Mk 6 and Mk 6 Mod 1, noted in NAVORD OTI M2-44, applies to Pistol and Extender Mechanism Mk 6 Mod 2 in the following respects and subject to appropriate and applicable information set forth in this publication:

(a) Pistol - paragraphs 3A(1), 3A(2), 3A(3), 3A(4), 3A(6), 3A(7), 3E3(1) 3B(2), 3B(3), 3B(4), 3B(5), 3B(6), 3B(8), 30(9), 30(10), 30(11), 3B(13), 3B(14), 3131(15) and 3C.

(b) Booster extender mechanism - 3A(8), 3A(10), 3A(11), 3A(12) and 3C.

19. Drawings, as listed in figures 15 and 16, have been prepared to completely describe the Pistol and Extender Mechanism Mk 6 Mod 2. Subassembly drawings are provided to show the grouping of various parts in accordance with manufacturer's assembly proce-dure. It is believed that this feature will be helpful to maintenance and overhaul activi-ties. Each part is detailed on a separate drawing of appropriate size, and all material re-quired for the production of the components is identified by drawings. In order to install this system of drawings, it was deemed advisable to redraw and renumber such parts of Pistol and Extender Mechanism Mk 6 and Mk 6 Mod 1 as are also used in the respective Components Mk 6 Mod 2. This action should not result in any confusion because original drawings of the interchangeable parts have been appropriately revised to record the identification shown on enclosures figures 15 and 16. Drawings, if required, may be ob-tained upon request to the Naval Gun Factory, Navy Yard, Washington, D.C.