Ammunition 5"/38 caliber gun

drawing of loaded semi-fixed round.

this gun uses semi-fixed ammunition. (pictured) (also called separated ammunition.) each round consists of projectile , powder case. 2 parts of round kept separate until gun. @ gun, first combined on rammer tray, , power rammed chamber 1 ram cycle. powder case fills volume of chamber, , length seats projectile s rotating band bore s rifling. different naval bag gun. in bag gun: (1) projectile, itself, power rammed chamber until rotating band seated in bore s rifling. (2) rammer retracted. (3) powder bags rammed in. different artillery field guns: (1) projectile hand rammed chamber ramrod until rotating band seated in bore s rifling. (2) ramrod retracted. (3) next powder placed in chamber either bag or primed canister required charge. note single ram operation used in semi-fixed guns decreases loading time, , therefore increases firing rate on medium , large caliber guns. example, each of 9 8 (203mm)/55 caliber rapid-fire guns installed on des moines-class cruiser used auto-loaded semi-fixed ammunition , had firing rate of 10 12 rounds minute. see 8 /55 caliber mark 71 gun.

projectile

5 /38cal anti-aircraft common (aac) projectile.

the projectile (pictured) has 3 major parts: body, fuze, , explosive charge.

projectile body

the body machined steel tube ogive shape @ 1 end. @ ogive , rear ends threaded openings used install shell s filler , hold fuzes. around tube near base copper alloy ring called rotating band. band has diameter larger bore, , when projectile , powder case rammed chamber, band jammed grooves of bore s rifling. forms gas seal between projectile , bore. also, projectile travels down barrel, band grips rifling impart spin projectile.

fuze

the fuse detonates projectile cause maximum damage target. different targets required different fuzes. safety requirements of fuze that...

... safe handle. (i.e.: not arm if dropped, rolled, or shook.)
... remains unarmed in bore, , until projectile clear of firing ship protect exposed personnel. therefore, when gun fired, following events take place:

14,000g acceleration burning propellant in bore. acceleration used setback (i.e.: force rear.) fuze parts unarmed armed positions due inertia.
centrifugal force 12,360 rpm projectile rotation. force causes other parts move outward.
7.2g deceleration aerodynamic drag after projectile leaves muzzle. due inertia, other movable parts creep forward.

all of these events must take place in correct order arm fuze.

list of fuze types:

mechanical time fuze
a nose time fuze detonates shell after adjustable time interval has elapsed since firing.
base detonating fuze
a base impact fuze screwed rear of projectile protect fuze during impact. delays shell s detonation 25 ms after impact, allowing projectile penetrate target prior detonation.
point detonating fuze
a nose impact fuze. fast detonation on surface of target.
vt fuze
the vt (variable time) fuze proximity fuze. nose electronic fuze not require impact trigger. designed detonate close target. intended used against air targets. used in shore bombardment , surface actions against fast boats. because vt fuze has proved suited bursting shell @ correct distance above ground or water maximum damage lightly armored targets on large area.
auxiliary detonating fuze
in projectile drawing, auxiliary detonating fuze screwed onto bottom of mechanical time fuze. because time fuze primer not have enough explosive shock detonate relatively insensitive explosive d . auxiliary fuze uses intermediate explosive set off time fuze primer, , in turn, sets off explosive d .


powder case

5 /38cal full service charge.

the powder case brass or steel alloy cylinder closed @ 1 end. holds propelling charge , case combination primer. charge held packed around primer wad, distance piece (not in clearing charge), , plug. when rammed in chamber projectile, full , reduced charge cases designed fill volume of chamber breechblock face base of projectile when rotating band jammed bore s rifling. in other words, powder case acts rammer extension projectile. there 3 types of powder cases:

full service charge (pictured)

a 26.7 inch (679 mm) long, 12.3 pound (5.6 kg) brass case 15.5 pounds (7.0 kg) of smokeless or flashless (used @ night) powder. full service charge new gun initial velocity 2,600 fps (792 m/s). used in surface , anti-aircraft actions.


reduced charge

the reduced charge uses same case full service charge, 3.6 lbs (1.6 kg) of power , longer distance piece. reduced charge new gun initial velocity 1,200 fps (366 m/s). used in shore bombardment lob shells, mortar, on obstacles hit targets on opposite side, , propelling star shells @ lower velocity protect parachute being shredded while deployed.


clearing charge (pictured)


5 /38cal clearing charge.





the clearing charge (also called, short round ) short case; plugged above wad. distance piece between wad , plug left out. powder charge less full service charge. case essential safety of mount because needed clear gun after misfire. due importance, kept in special container in mount whenever ship in combat zone. misfire dangerous in semi-fixed guns. when breech opened after misfire, faulty powder case can extracted, projectile remain jammed in rifling. also, or part of extracted case s cork plug may still wedged in chamber behind projectile. fouls chamber because decreases chamber s volume. and, since full , reduced charge cases take full volume of unfouled chamber (see loaded semi-fixed round drawing above), residue left extracted case prevent them loading chamber. therefore, clearing charge made short fit fouled chamber.






after hand extracting bad case chamber, clearing charge removed special container , hand rammed chamber. clearing charge sealed in chamber, projectile fired out muzzle. important clear projectile through muzzle because not easy nor safe pushing bore rod down barrel force fuzed projectile through chamber , gun house. also, if gun has fired number of rounds prior misfire, time critical because barrel may hot enough cook off high explosive in projectile. destroy mount.






^ cite error: named reference navordandgunv1 invoked never defined (see page).
^ navy weapons definitions pt. 2 . retrieved 2013-09-06. 
^ cite error: named reference gm3 invoked never defined (see page).
^ cite error: named reference navweaps invoked never defined (see page).
^ naval ordnance , gunnery, volume 1, naval ordnance, navpers 10797-a (1957 ed.). washington 25, d.c.: u.s. navy, bureau of naval personnel. 1957. p. 29. 3 primary functions of rotating band seal bore, position , center rear end of projectile, , impart rotation projectile. 
^ naval ordnance , gunnery, volume 1, naval ordnance, navpers 10797-a (1957 ed.). washington 25, d.c.: u.s. navy, bureau of naval personnel. 1957. ... time fuzes clockwork mechanisms used obtain timed air bursts. 
^ naval ordnance , gunnery, volume 1, naval ordnance, navpers 10797-a (1957 ed.). washington 25, d.c.: u.s. navy, bureau of naval personnel. 1957. radio proximity or vt fuze used in of types of projectiles can use mechanical time fuzes... 
^ naval ordnance , gunnery, volume 1, naval ordnance, navpers 10797-a (1957 ed.). washington 25, d.c.: u.s. navy, bureau of naval personnel. 1957. point detonating, time, , vt fuzes may called nose fuzes ... 
^ naval ordnance , gunnery, volume 1, naval ordnance, navpers 10797-a (1957 ed.). washington 25, d.c.: u.s. navy, bureau of naval personnel. 1957. vt-fuzed ammunition effective on exposed personnel , lightly armored targets ... 
^ cite error: named reference 5/38 invoked never defined (see page).
^ naval ordnance , gunnery, volume 1, naval ordnance, navpers 10797-a (1957 ed.). washington 25, d.c.: u.s. navy, bureau of naval personnel. 1957. in 40 mm , larger guns, cardboard disc, or wad, forced case , distance piece, if 1 needed, placed on top. 
^ naval ordnance , gunnery, volume 1, naval ordnance, navpers 10797-a (1957 ed.). washington 25, d.c.: u.s. navy, bureau of naval personnel. 1957. whether gun hot or cold, risks attendant upon removing loaded , fuzed projectile seated in bore, backing out, considered unwarranted... 
^ naval ordnance , gunnery, volume 1, naval ordnance, navpers 10797-a (1957 ed.). washington 25, d.c.: u.s. navy, bureau of naval personnel. 1957. loaded , fuzed projectile, seated in bore of gun hot previous firing, presents hazard, since detonation of projectile possible result of being heated.