THEORY OF OPERATION :: COLT .45 ACP GOVERNMENT MODEL PISTOL :: (Series 70 and earlier models)
by Richard M. Bash

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

DISCONNECTOR, SEAR, SEAR SPRING AND SAFETY LOCK OPERATION

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 90x bend at two places in the spring. The bottom end of the spring has a 90x 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 90x 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.



COLT .45 ACP PISTOL PARTS LIST

1. Barrel 2. Barrel bushing 3. Barrel link 4. Barrel link pin 5. Disconnector 6. Ejector 7. Ejector pin 8. Extractor 9. Firing pin *10. Firing pin plunger 11. Firing pin spring 12. Firing pin stop 13. Front sight 14. Grip safety 15. Hammer 16. Hammer pin 17. Hammer strut 18. Hammer strut pin 19. Magazine assembly 20. Magazine catch 21. Magazine catch lock 22. Magazine catch spring 23. Magazine follower 24. Magazine spring 25. Main spring 26. Main spring cap

27. Main spring cap pin 28. Main spring housing 29. Main spring housing pin 30. Main spring housing pin retainer *31. Plunger lever 32. Plunger spring *33. Plunger spring - firing pin 34. Plunger tube 35. Rear sight 36. Receiver **37. Recoil spring 38. Recoil spring guide 39. Recoil spring plug 40. Safety lock 41. Safety lock plunger 42. Sear 43. Sear pin 44. Sear spring 45. Slide 46. Slide stop 47. Slide stop plunger 48. Stocks - left and right 49. Stock screw (4) 50. Stock screw bushing (4) 51. Trigger assembly *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.

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