View Full Version : Replacing the Mainspring on Colt Lawman III

April 27, 2011, 02:53 AM
I finally got to do some shooting over the weekend and one of them was my Colt Lawman III. I've never gotten to shoot this gun so I was looking forward to it, however I was quite surprised when I loaded up and pulled the trigger and the gun failed to go off. I waited enough time and tried again, nothing. Ok, open the cylinder. Well two of the rounds primers have dents in them but didn't fire. Next, tried SA. BANG! That works so I'm thinking the mainspring is too weak to fire the rounds. If I'm wrong please point out what I'm missing and if I'm correct I could use some steps on how to replace the spring. Thank you.

James K
April 27, 2011, 10:47 AM
The Lawman III is one of the new design Colt DA revolvers; it uses a coil mainspring (hammer spring) which is fairly easy to replace. Check www.gunpartscorp.com for the part.

But before doing so, how about the ammo? Is it fairly fresh and has it worked OK in other guns.? Most of the time, misfires are due to the ammo, not the gun. (Don't be deceived by the seeming shallow dent in the primer; the dent in a dead primer looks shallow because when the primer fires, its metal flows back around the firing pin, making the dent look deeper than it is.)


April 27, 2011, 06:45 PM
Here's how to replace the Mark III mainspring:

Mark III mainspring change-out is fairly easy.
You'll need the following:
A gunsmith's screwdriver that will fit the grip screw.
A paper clip or drill bit.
A wood block with a hole drilled into it about 1 1/2" inches.
Some rust preventing lubricant like CLP Breakfree.
Some grease.

With the grips off, cock the hammer ALL the way back and hold it.
Look at the mainspring guide and you'll see a small hole in the end BELOW the mainspring seat plate.
Stick the paper clip or small drill shaft through the hole.

Holding the hammer, pull the trigger and ease the hammer all the way forward.

Grab the mainspring seat plate and pull it to one side and turn the plate until you can slip it out of it's seat grooves in the frame.

Put the rounded head of the mainspring guide into the hole in the wood block.
This allows you to maintain control as you replace the spring and prevents things flying away.
(Wear safety glasses).

Gripping the mainspring seat TIGHTLY, force the plate down on the guide until you can pull the pin out of the guide.
CAREFULLY ease up on the plate until the tension is off the spring.
Remove the spring from the guide.

Use a solvent like lacquer or paint thinner to clean the parts, including the new spring to remove old storage lubes.
Dry them thoroughly, then apply a THIN coat of CLP Breakfree to all parts, including the spring, to prevent rusting.

Apply a coat of grease to the mainspring guide shaft to lubricate it and the spring.

Put the guide and new spring in the hole in the wood block, grip the seat plate TIGHTLY and force it down over the spring and guide until you can get the disassembly pin back into the guides hole.

Apply a dab of grease to the rounded head of the mainspring guide.

Insert the guide up into the frame with the short end toward the front.
(The hole in the seat plate is drilled closer to one end of the plate. You want that end facing toward the barrel).

Push and turn the seat plate until you can slip it into the guide grooves in the frame.

With the retaining pin still in place test the hammer to insure everything is properly in place before removing the pin.

April 27, 2011, 07:39 PM
Thank you for the replies. Jim, I did think about the ammo but it fired just fine in my S&W 36 that day for both SA and DA.