Detailed re-assembly of the 1911

Having detailed the complete disassembly of a 1911, it’s only fair to show you how to put it back together.  Much of the process can be considered “disassembly in reverse”, but there are some details that we need to pay attention to that were ignored in the teardown.

We’ll start with the slide.

Push the extractor back into position.  Note that the hook should face into the pistol.  The back of the extractor is such that it won’t go in correctly in the wrong orientation.  Align the slot at the rear of the extractor, with the slot for the firing pin stop.

Slot in extractor which allows the firing pin stop to lock it into position


Extractor slot lined up with slot in slide

You can push the firing pin stop into position to help guarantee the alignment of the slide and ejector slots.

Insert the firing pin and firing pin spring (spring forward) into the slide.  Push it down and hold it in place with the tip of a punch, while starting the firing pin stop into position.  As soon as the firing pin stop covers part of the firing pin hole, the firing pin is trapped and you can focus on pushing the stop fully into place.

The firing pin stop has just been started into position, and is at the point where the firing pin is trapped

The firing pin stop is fully installed when the back of the firing pin "pops" through the hole in the firing pin stop

Note the orientation of the trigger.  The slope at the back of the trigger bow should follow the slope of the back of the pistol.  Insert the trigger into its channel, pushing it all the way forward.

Proper trigger orientation

Now re-assemble the magazine release (you should be able to see what’s going on now that it’s out of the frame) then re-insert it into the frame.  Hold it in the slightly depressed position and turn the ‘screw’ clockwise 1/4 turn.

Magazine release replaced.

The disconnector and sear go back in the frame as a pair.  It’s easy to remember the orientation, if you understand the function of each, so let’s look at that for a moment.  The disconnector sticks through a hole in the frame where the slide can push on it.  It has an elongated pin hole that allows it to move up and down, disconnecting the sear from the trigger.  It does this when the slide runs over the part of the disconnector that protrudes through the frame i.e. when the slide cycles.  The blade of the disconnector is pushed off of the sear and it cannot return until the trigger is released.  This is what prevents the hammer from falling when the trigger is held to the rear.  It also prevents the pistol from being fired before the slide is in battery.

The oversize slot in the disconnector allows it to move up and down, disconnecting the trigger from the sear.

The round end of the disconnector sticks up through the frame and pushes against the slide. When the slide is in battery, the tip is in a slot in the slide, but when the slide cycles, it pushes down on the disconnector.

The back of the disconnector has a ramp which the middle finger of the 3-finger spring pushes on.  Pressure on the ramp makes the disconnector want to travel upward, where it can again engage the sear.  When re-assembling, the disconnector ramp should be to the rear of the pistol, and the flat portion of the disconnector should rest on the rear of the trigger bow.

This angle at the bottom of the disconnector is a surface for the middle 'finger' of the 3-finger spring to bear on. This causes the spring to push the disconnector up when the slide is not forcing it down.

The sear has a a ‘sharp’ edge that engages the hammer, these are the actual sear surfaces.

The 'sharp' edge of the sear - the part that engages the hammer and holds it in the cocked position.

The other end has two ‘legs’ which hook to the disconnector when the disconnector is in the ‘up’ position.  In that position, the disconnector connect the trigger to the sear, allowing the trigger to release the sear engagement, firing the pistol.


The "legs" of the sear which are engaged by the disconnector.

The sear and disconnector assembled together in the correct orientation. In this position, the pistol would point to the right.

Assemble the disconnector and sear together, as shown.  Insert the tip of the disconnector into the frame until it pushes (slightly) through the hole in the top of the frame.  A punch may be used to align the disconnector and sear holes.   The sear surface (sharp edge) of the sear should point to the top rear of the pistol, the flat blade at the bottom of the disconnector should rest on the back of the trigger bow.

Insert the sear pin, being sure that it traps both sear and disconnector in place.

The punch is pointing a little past where the top of the disconnector sticks through the frame.

Take a minute to look at the relationship of the disconnector, trigger bow, and sear.  Imagine the sear holding the hammer back.  If you push the top of the disconnector down, you can see, by pulling the trigger, that there is no longer a connection between the trigger and sear.

The disconnector in the down position, as it would be while the slide cycles. You can see that the disconnector no longer touches the sear, so the trigger can no longer activate it.

When the sear is disconnected, two things must happen to re-connect the trigger and sear.  The slide must move into battery, positioning the notch in the slide over the top of the disconnector, giving it space to move upward and the trigger must be released, allowing the disconnector to slip behind the legs of the sear.  (The disconnector cannot move upward until it can get behind the legs of the sear).

If you then push the disconnector up a little bit, you will see that the bottom of the disconnector bridges the gap between disconnector and sear, and pulling the trigger, moves the sear.

The disconnector in firing position. Note that it now connects the trigger bow to the legs of the sear. If the trigger bow moves back, the bottom of the sear is also pulled back.

Install the hammer.  Simply push it into alignment with the hammer pin hole, and insert the hammer pin.  Note that the outermost hole is for the safeties.

The re-installed hammer.

Now, insert the 3-fingered spring.  Push the hammer stirrup out of the way.  At the bottom of the 3-fingered spring, the spring is bent to leave a small (~1/32″) tab.  Insert this into the slot in the back of the frame and lay the spring flat.  Hold the bottom of the spring in place with your thumb.

The bottom of the three-fingered spring is bent, forming a small tab which is inserted into a slot in the frame.

The slot in the frame, in which the tab on the three-fingered spring is inserted.

Note the function of the fingers.  The left finger pushes on the sear, holding it in engagement with the hammer.  The middle finger pushes on the disconnector ramp, causing the disconnector to want to travel ‘up’ as previously described.  The right finger is what pushes the grip safety back, when it is not depressed.  The left and middle spring, therefore, contribute to the weight of your trigger pull.  The right finger does not.

With the three-fingered spring in place it's possible to see the function of two of the three fingers.

Push the mainspring housing about half-way into place to hold the 3-fingered spring in position.

Pushing the mainspring housing part way on traps the three-fingered spring and holds it in place.

Replace the spring plungers for the slide stop and thumb safety.  They will only go in one way.

The thumb safety and slide stop spring plungers re-inserted in the plunger tube.

Push the grip safety into position.  Holding it in position, using a firing grip, start the thumb safety into it’s hole.

The thumb safety is started into its hole, capturing the grip safety.

Place the hammer in a cocked position.  Push the thumb safety in until it touches the spring plunger.  The plunger must be depressed to allow the safety to go all the way in.  Recall that the safety will only go in when it is held in a position between the fire and safe positions.  Applying pressure to the thumb safety, depress the plunger with a 1/16″ punch.  When the position of the safety lines up, and the spring plunger is sufficiently depressed, the safety will snap into position as far as the punch will allow it.  Withdraw the punch, the plunger should now be held in place by the thumb safety.  Push the thumb safety all the way in.  This process is very simple with practice.

Installing the thumb safety while holding the spring plunger depressed.

Place the thumb safety in a firing position, depress the trigger and move the hammer to the fired position.  Being sure that the hammer stirrup is in the notch in the center of the grip safety, and that it enters the hole in the top of the mainspring housing, push the mainspring housing fully into place, and secure it by replacing the mainspring housing pin.

The mainspring housing pin is held in place by a plunger at the bottom of the mainspring.  As such it will have to be tapped into place with a soft-faced mallet.

The mainspring housing is pushed into position and pinned in place.

If you have a Springfield ILS mainspring housing, cock the hammer and remove the pin from the back of the mainspring housing.

At this point, all that remains is putting the stock scales in place and screwing them back on.

Scales replaced.

The pistol is now back to a field-stripped level.

Before firing the pistol, it should be re-assembled completely and function tested.  To function test:

  1. Test that the pistol will not fire if the grip safety is not depressed.  (Put the thumb safety in the fire position, cock the hammer, and pull the trigger without depressing the grip safety.  The hammer should not fall.
  2. Grasp the pistol in a normal firing grip, depressing the grip safety, with the hammer cocked, but the thumb safety in the ‘safe’ position.  Apply firm (but not excessive) pressure to the trigger.  The hammer should not fall.
  3. Remove your finger from the trigger, move the thumb safety to the ‘fire’ position.  the hammer should not fall.
  4. Continuing, from the previous step, pull the trigger to the rear, and hold it back.  The hammer should fall.
  5. Continuing to hold the trigger to the rear, cycle the slide.  The hammer should be cocked, and remain cocked even though the trigger is held to the rear.
  6. Release the trigger and squeeze it again, the hammer should fall.

This simple test provides evidence that the grip safety, thumb safety, sear, trigger and disconnector are all properly re-assembled.

The definitive reference to 1911 assembly and disassembly are the Kunhausen manuals.  I’m linking to Amazon, because there description provides complete info, but you should be able to find this book (and it’s companion Volume II if desired) for $35-$40 if you shop around.
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One Response to Detailed re-assembly of the 1911

  1. Scott C says:

    Nice work! The hardest part for me when first learning how to do a detailed strip was the installation of the sear/disconnector. I use a small punch to align and then insert the pin. I find this makes it easy for me.

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