Light, compact, accurate, and a natural pointer, the Colt 1903 Pocket Auto retrofitted with modern sights remains a great little pistol, but a difficult one to reassemble. The manuals I’ve seen either say “assembly is the reverse of disassembly”…which ain’t so…or not to disassemble beyond field stripping…or to take it to a gunsmith. Fine…except where does the gunsmith go for guidance? So when I got one of these in (as a bag of parts) to replace the slide safety, mainspring and trigger all broken or bent by an owner’s disassembly attempts, I thought I’d document how to reassemble one of these for the benefit of the next guy.



Field stripping is easy and you can find how to do it in books. I’ll only cover the parts internal to the frame. Here I’ve already installed the trigger, sear and disconnector, which are also straightforward. Also note that I’m using a rubber band to prevent the ejector from pivoting, which will make aligning the hammer easier.



The first parts to go in are the magazine catch and the sear spring. Both are straightforward…the magazine catch has a tenon that fits in a rectangular slot in the frame and the sear spring in the lower of two circular recesses in the frame sides. After installation, apply pressure to the spring with your finger to insure the three upper leaves engage the rear surfaces of the sear and disconnector and the lower leaf the magazine catch, and that all function correctly.



Note the upper circular recesses in the frame. These are for the mainspring, but are a sloppy fit until the mainspring is compressed, so watch the alignment as you proceed.



Slide the mainspring upward into the frame its position controlled the recesses. Note I’ve lightly mounted the pistol in a bronze-lined vise for stability.



Next I remove the mainspring temporarily to check the position of the sear before installing the grip safety. The sear must be tilted to the rear (push the lobes down) to properly engage the hooks on the grip safety in relationships shown in the diagram below:



Note how the three leaves of the sear spring (28) engage the sear (22) and disconnector (23), how the upper mainspring leaf (29) fits into the hammer slot above the pinned roller (18), and how the hooks of the grip safety (27) engage the rear lobes of the sear.



I slide the grip safety into the frame. Note that pressing against the mainspring will cause the bend of the mainspring to seat into the recess milled into the grip safety. I lightly greased both faying surfaces to make that easier.



Here I’ve seated the mainspring by applying pressure to the lower end of the grip safety, and am holding the assembly in place using a rubber band. Note the upper rear face of the grip safety rests firmly against the mortise in the frame. For future reference, this is the “cocked” position of the grip safety.



If instead, your efforts result in the grip safety ending in the “fired” or hammer-down position, the upper grip safety hooks rode over the sear lobes. You need to remove the grip safety, tip the sear to the rear and reinstall the grip safety so the end result is the “cocked” position.



An alternative to using a rubber band to hold the grip safety in position is to use a thin slave pin. Keep in mind that the more play there is in the bottom of the grip safety, the less pressure is required for the hammer to engage the upper leaf of the mainspring, which is the next step.



Here I’m pointing to the upper leaf of the mainspring as it bears against the grip safety. I apply some grease to the upper leaf, and to the roller and other faying surfaces on the hammer.



Here I’ve mounted an undersized slave pin for the hammer in the vise. This one happens to be a punch. I ease any burs and apply some grease to the punch for an easy sliding fit.



Again insuring the grip safety is in the “cocked” position, I press both the grip safety and the trigger using my right hand and tilt the sear all the way forward by pushing the bottom of the sear rearward using my pointer with my left.



With right-hand pressure still on the grip safety and trigger, I use the tip of a punch to push down the disconnector, again using my left hand. These steps are critical for aligning the hammer. Here you see the hammer resting loosely in place – it hasn’t been installed yet.



Now while continuing pressure on trigger and grip safety, I place the hammer roller between the mainspring leaf and the inside surface of the grip safety, pressing the hammer down onto the leaf using my left thumb. Refer to the drawing above – I’m sliding the roller behind the mainspring leaf until the leaf bottoms out in the hammer slot. This requires moderate to heavy pressure – just insure you don’t oversqueeze the trigger at the same time, or you can bend its rails.



Then while continuing pressure at all three points, I carefully lift the frame and fit the assembly over the undersized slave pin I secured in the vise. The slide safety also serves as the hammer pin, and fits through two opposed holes in the frame, two more opposed holes in the ejector, plus the hammer itself. It’s a difficult fit – insure no faying surfaces are burred and apply grease to the hammer sides, holes and pin.

While applying downward pressure to the hammer to keep it engaged with the mainspring leaf, I also have to rotate the hammer forward to the downward position to properly align all the holes. All with the sear tipped forward and the disconnector pressed downward. Until you get the hang of it, you may find it useful to use a small-diameter slave pin like the one shown in the photo above. Here I’ve installed the slave pin and am testing the hammer to insure it is properly engaged with the mainspring.



When I’ve mastered the sequence necessary to align all the holes while keeping the hammer and mainspring correctly engaged, I remove the hammer and switch to a slave pin that is only slightly undersize.



Then with the slave pin still secured in the vise, I rotate and pull upward on the frame to withdraw the slave pin half-way, then tilt the frame as necessary to sight down and align the holes so I can push in the slide safety-hammer pin until it touches the slave pin. When it does, I continue the sequence until the hammer pin completely replaces the slave pin. Note that the stud on the slide safety only installs in the “safe” position.



With the slide safety-hammer pin fully seated, I replace the lower slave pin with the magazine catch pin, double check that the grip safety, slide safety, hammer, trigger and magazine catch are all functioning correctly, reassemble the remaining parts, and test fire the pistol. My first test-fire rounds are a series of single rounds singly-loaded to insure the sear is catching the hammer correctly and the pistol won’t double or triple when a full magazine is loaded.

Good info and good of you to pass it on down the line.

I'll second the thank you for going to the trouble of posting this. I've had to put these back together on occasion but usually so much time has passed since the last one that the only part I remember is how much I hate doing it. Hopefully your post will make it go smoother in the future.

I have one on the way that was made in 1908 and looks as though it was never cleaned, not looking forward to it but this certainly will help, thank you.

Where were you a year ago when I got one in for a blue job. Had to invent a few new swear words before I got it reassembled. Bill

Another tip from the S&W forum is from a smith in Houston who uses strong, pencil-sized magnets to hold the sear, sear spring and magazine catch in position during assembly.

If you save this post as a web archive it will always be on your computer for future reference