                           Combat Arms
                         2869 Grove Way
              Castro Valley, California 94546-6709
                    Telephone (415) 538-6544


            ͻ
                                                  
                     THEORY OF OPERATION          
             COLT .45 ACP GOVERNMENT MODEL PISTOL 
                (Series 70 and earlier models)    
                                                  
            ͼ


     Each time a cartridge is fired, the parts of the pistol
function in a given order. The cycle of functioning is divided into
eight steps. It should be kept in mind that more than one step may
occur at the same time. Assume for the purposes of this discussion
that a loaded magazine is in the weapon and a live cartridge is in
the chamber. The hammer is fully cocked, the safety lock is off,
the grip safety is depressed, the trigger is squeezed and the round
is ignited. The cycle of functioning begins.

1.   Feeding
     As the slide moves to the rear due to the force of recoil, the
     underside of it clears the top of the magazine. The magazine
     follower, under pressure from the magazine spring, forces the
     top round up against the lips of the magazine. This places the
     top round in position to be picked up by the face of the slide
     during its forward movement.
     
2.   Chambering
     At the termination of the rearward movement of the slide, the
     expanding recoil spring forces the slide forward. The lower
     portion of the face of the slide passes between the lips of
     the magazine, strips the top cartridge from the magazine and
     pushes it to the bullet ramp and up into the chamber. During
     this movement, the base of the cartridge slides up the face
     of the slide. At this time, the extractor enters the
     extracting groove in the head of the cartridge. Chambering
     is complete when the cartridge is fully seated in the chamber
     and the face of the slide is against the rear extension of
     the barrel.

3.   Locking
     After chambering is completed, the slide continues forward and
     pushes the barrel forward. As the slide continues to exert
     force against the rear of the barrel, the barrel pivots up and
     forward of the barrel link. At this time, the locking ribs on
     the barrel enter the locking recesses in the underside of the
     slide. The forward movement of the recoiling parts terminates
     when the barrel lugs strikes the slide stop pin.

4.   Firing
     When the grip safety is depressed and the trigger is squeezed,
     the trigger bar presses against the disconnector which in turn
     transmits this movement to the sear. The sear rotates on the
     sear pin and disengages from the full cock notch of the
     hammer. The expanding mainspring pushes the hammer strut up,
     rotating the hammer to rotate forward on the hammer pin and
     strike the firing pin. The inertia firing pin travels forward,
     compressing the firing pin spring. The firing pin moves
     through the firing pin well in the face of the slide and
     strikes the cartridge's primer. The primer ignites the
     propellant and the expanding gases force the bullet through
     the barrel. The firing pin spring expands and withdraws the
     firing pin from the face of the slide.

5.   Unlocking
     As the gases expand, equal pressure is exerted in all
     directions. These gases force the bullet down the barrel and
     force the slide to the rear. As the slide moves to the rear,
     it carries the barrel with it. The barrel link pivots about
     the slide stop pin, which is attached to the stationary
     receiver, and draws the barrel downward as well as to the
     rear. As the barrel is pivoted downward, the barrel locking
     ribs are disengaged from the locking recesses in the slide and
     unlocking is completed.

6.   Extracting
     The slide continues its rearward movement and the extractor,
     engaged in the extracting groove of the cartridge, withdraws
     the cartridge case from the chamber. Extracting is completed
     as the cartridge clears the chamber.

7.   Ejecting
     As the slide continues to move to the rear, the cartridge
     case, which is held against the face of the slide by the
     extractor, strikes the ejector on the receiver, pivots on the
     extractor and is ejected from the pistol through the ejection
     port.

8.   Cocking
     Cocking begins as the slide starts rearward in recoil. The
     firing pin stop pushes the hammer rearward and the hammer
     strut is pushed down against the mainspring cap, compressing
     the mainspring. Rearward movement of the slide terminates as
     the lower projection of the slide strikes the recoil spring
     guide. The expanding recoil spring causes the slide to begin
     its forward movement. As the slide moves forward, the hammer
     follows the slide for a short distance; then the sear, which
     is bearing against the hammer through the action of the sear
     spring, enters the full cock notch of the hammer and holds it
     in the cocked position. When the slide is fully forward and
     the trigger is released, the disconnector positions in its
     recesses in the bottom of the slide and cocking is completed.

Source for the above information: Guidebook for Marines - 14th
edition

      
ͻ
                                                           
DISCONNECTOR, SEAR, SEAR SPRING AND SAFETY LOCK OPERATION  
                                                           
ͼ


DISCONNECTOR
1.   The disconnector sits forward of the sear. There is a paddle
     on the bottom of the disconnector. When the slide is in
     battery (at its most forward position), the top of the
     disconnector rides up to fit in a 0.4 inch long slot in the
     bottom of the slide. The "rest" or "up" position of the
     disconnector causes the top of the disconnector to be exposed
     about 0.06 inches above the frame.

2.   The paddle area of the disconnector is pressed by the
     disconnector spring prong against the back of the trigger bow.

3.   When the slide is in battery with a live round in the chamber,
     the hammer cocked, the safety lock off, the grip safety
     depressed and the trigger pulled, the rear lateral bar of the
     trigger bow presses against the front side of the
     disconnector's paddles. The disconnector begins to pivot
     around the sear pin. As the rear side of the disconnector's
     paddles move aft, they contact the forward side of the sear's
     feet. The sear's feet move rearward as the sear begins to
     pivot, along with the disconnector, around the sear pin. As
     the sear's feet are pushed rearward, the sear's beveled nose
     moves forward. The beveled nose is engaged in the hammer's 
     notches. When the sear has been rotated enough to cause the
     sear's beveled nose to withdraw from the hammer's full cock
     notches, the hammer, under mainspring pressure directed up the
     hammer strut, moves rapidly forward. The hammer strikes the
     firing pin, which in turn strikes the primer, and the
     cartridge is fired.
     
4.   When the slide is drawn rearward, whether manually or by the
     force of the recoil, the top of the disconnector is pressed
     downward. The paddles at the bottom of the disconnector, which
     normally rest just in front of the bottom feet of the sear,
     move downward as the top of the disconnector is depressed by
     the slide and the disconnector's paddles clear the feet of the
     sear, When the disconnector's paddles clear the sear's feet,
     pulling the trigger will not move the sear at all.

SEAR
1.   The purpose of the sear is to hold the hammer back by having
     the sear's beveled nose inserted into either the half cock or
     full cock notches of the hammer. When the sear is in the half
     cock notch of the Series 70 and earlier pistols (with the
     safety lock off and the grip safety depressed), pulling the
     trigger will not cause the sear to move out of the half cock
     notches and permit the hammer to fall. In the Series 80
     pistols, pulling the trigger with the hammer at the half cock
     position will permit the hammer to safely fall to the "rest"
     position.

2.   When the sear is in the full cock notches of the hammer (with
     the safety lock off and the grip safety depressed), pulling
     the trigger causes the sear's nose to move out of the full
     cock notches and permit the hammer to fall against the firing
     pin.

SEAR SPRING
1.   The sear spring is a three pronged spring which fits into a
     slot in the mainspring housing area at the rear of the frame.
     The left spring prong is the actual sear spring, the center
     prong is the disconnector spring and the right prong is the
     grip safety spring. There is a 90 bend at two places in the
     spring. The bottom end of the spring has a 90 bend in it to
     permit it to slip into the slot in the rear of the frame. This
     acts to anchor the spring unit. The other 90 bend is on the
     sear spring prong and is provided to permit the spring prong
     to ride on the minimum possible surface area of the sear's
     left foot.

2.   The sear spring prong presses forward against the rear of the
     left sear foot, which causes the sear's beveled nose to push
     rearward with force. This engages the sear firmly in the
     hammer's notches.

3.   The disconnector spring prong presses forward against the rear
     center of the disconnector's paddle area. This moves the
     paddles forward and positions the disconnector's paddle area
     about 0.2 inches forward of the rear of the sear's feet. The
     front of the disconnector paddle area presses forward against
     the rear of the lateral bar on the trigger bow and forces the
     trigger to move to its most forward position. Thus, the
     disconnector spring prong acts as a trigger return spring as
     well as serving to rotate the paddles of the disconnector
     forward of the sear's feet.

4.   The grip safety spring prong is arched rearward. The tip of
     the grip safety spring prong rides below a bar on the right
     forward side of the grip safety. The grip safety pivots about
     the safety lock pin. The bar on the right forward side of the
     grip safety has a cutout in it, creating a protruding tip. 

     When the pistol is at rest with no forward pressure being
     applied against the rear of the grip safety, the rearward
     acting pressure of the grip safety spring prong pushes against
     the forward side of the grip safety. This causes the top of
     the grip safety to pivot forward. As it pivots forward, and
     the rear section of the grip safety pivots rearward, the tip
     of the bar on the right forward side side of the grip safety
     lowers against the right side of the rear of the lateral bar
     on the trigger bow. Because the tip is aligned behind the
     trigger bow, the trigger cannot be pulled.

     When the grip safety is being normally depressed by the web
     of the shooting hand, the lower section of the grip safety
     pivots forward (the top section pivots rearward) and the tip
     of the bar on the right forward side of the grip safety moves
     above the lateral bar on the trigger bow. Since there is now
     no restraint against the trigger bow, the trigger may be
     pulled rearward to fire the weapon.

     As soon as the forward acting pressure from the web of the
     shooting hand is released, the grip safety pushes rearward
     against the grip safety body and again causes the pivoting
     action of the grip safety to position the tip of the bar
     against the rear of the trigger bow. 

SAFETY LOCK
1.   The safety lock is located on the left side of the frame. Its
     purpose, when engaged, is to prevent the sear from moving when
     the trigger is pulled and the hammer is in the full cock
     position. On the inside portion of the safety lock is a stud
     which will move to the shoulder area of the sear (that portion
     of the sear directly above the feet) when the safety lock is
     moved upward to the engaged position. The safety lock cannot
     be engaged unless the hammer is in the full cock position.

               ͻ
                                               
                COLT .45 ACP PISTOL PARTS LIST 
                                               
               ͼ
           
  1.  Barrel                          27.  Main spring cap pin
  2.  Barrel bushing                  28.  Main spring housing
  3.  Barrel link                     29.  Main spring housing pin
  4.  Barrel link pin                 30.  Main spring housing pin
                                           retainer
  5.  Disconnector                   *31.  Plunger lever
  6.  Ejector                         32.  Plunger spring
  7.  Ejector pin                    *33.  Plunger spring - firing
                                           pin
  8.  Extractor                       34.  Plunger tube
  9.  Firing pin                      35.  Rear sight
*10.  Firing pin plunger              36.  Receiver
 11.  Firing pin spring             **37.  Recoil spring
 12.  Firing pin stop                 38.  Recoil spring guide
 13.  Front sight                     39.  Recoil spring plug
 14.  Grip safety                     40.  Safety lock
 15.  Hammer                          41.  Safety lock plunger
 16.  Hammer pin                      42.  Sear
 17.  Hammer strut                    43.  Sear pin
 18.  Hammer strut pin                44.  Sear spring
 19.  Magazine assembly               45.  Slide
 20.  Magazine catch                  46.  Slide stop
 21.  Magazine catch lock             47.  Slide stop plunger
 22.  Magazine catch spring           48.  Stocks - left and right
 23.  Magazine follower               49.  Stock screw (4)
 24.  Magazine spring                 50.  Stock screw bushing (4)
 25.  Main spring                     51.  Trigger assembly
 26.  Main spring cap                *52.  Trigger bar lever

NOTES

*   This part is found only on Series 80 pistols and not on
    earlier versions of the Colt .45 pistol
**  The Officer's Model has two recoil springs that are different
    from each other.


The material in this file has be compiled by Richard M. Bash of
Combat Arms, 2869 Grove Way, Castro Valley, California 94546-6709,
telephone (415) 538-6544. If you have questions concerning the .45
ACP pistol, regardless of its manufacturer, please do not hesitate
to call me at the shop. Store hours are from 10 a.m. until 6 p.m.
Tuesday through Sunday and closed on Mondays.

Your courtesy in uploading this file to other bulletin boards will
be appreciated. Your comments are always welcomed. Thank you.
