Disassembly Diagram
From Late Instructions for the Model M

To Disassemble

To dismount barrel and slide: Remove magazine. Press in grip safety and cock the arm by drawing back the slide, (be sure to look and see that no cartridge remains in the chamber.) Then, holding the pistol as illustrated, move slide to rear in manner shown until the arrow indicator reaches the position indicated. (The perpendicular line on the slide at the arrow point should coincide with the front edge of the frame). Turn the barrel to the left as far as it will go. The slide (with barrel) may then be drawn forward from the receiver. The retractor spring and guide are then free.

If it is desired to remove the barrel from the slide, turn the barrel back to first position; it may then be drawn forward and removed.

To dismount barrel without removing the slide: Proceed as above; after turning barrel to left, release slide slowly to normal position, then turn barrel to right (original position) and pull out.

To remove firing pin: The firing pin can be removed by driving the pin out of the
slide with a concave punch. The firing pin assembly should come out of the rear of the firing pin housing.

To disassemble the magazine: The magazine can be disassembled by depressing the follower about an inch and a half with a pencil (eraser end) and then inserting an unbent paperclip into one of the side viewing holes to hold the tension of the spring. The follower should drop out the top and the tension of the spring can then be carefully released.

Detailed Disassembly

Detailed disassembly steps (Colt1903detail.pdf)
password to open: coltautos.com

To Assemble

To assemble barrel and slide: Insert the barrel in the slide with the locking ribs downward (i.e., in sight as you look into the slide). Give the barrel more than a quarter turn so that the ribs will fit into the recess made in the upper part of slide to receive the same.

Fit the slide and receiver so that the guides in receiver will engage in the slide grooves, taking care to have the forward end of the retractor spring enter the recess made to receive it in the lower part of the slide; draw back the slide to the position as shown by the indicators in illustration above, moving the barrel very slightly so it will engage, when it may be turned as far as possible to the right -- the arm is then fully locked and the slide will move forward to its closed position. Insert the magazine.

To replace barrel (slide remaining on receiver): Push barrel in until front end of center guide band is slightly in rear of front end of slide; then twist to left one-quarter revolution. Proceed as directed for replacing barrel and slide.