Friday, December 6, 2013

Trigger job for a Ruger



Smith & Wesson and Colt Revolvers have always had a reputation for having great triggers. This is mostly due to the work put in at the factory. Ruger has improved the triggers on their double action revolvers over the years, but most agree, they could use some work.

The subject of this trigger job is a Ruger SP-101 .357 revolver.

First let's discuss what makes up the trigger.

The trigger is both a noun and a verb. There is a part in every gun known as the trigger, it is human-machine interface that is manipulated by the user to operate the gun. A trigger is also the action involved between the interface and the internal components that cause the gun to fire. 

There are two types of triggers and trigger pulls: Single Action in which the trigger's sole job is to release the hammer, allowing it to strike the primer (the hammer must be manually cocked before pulling the trigger) and Double Action. In a double action gun, the trigger both cocks and releases the hammer, most double action guns will have a hammer spur, allowing the user to fire the gun in single action (by cocking the hammer manually) and double action. Single action trigger pulls are always lighter as they do not have to overcome the resistance of the hammer spring.

The felt resistance to movement is not the only factor in determining what is a good "trigger", there are other considerations like:

Take-up: This is the amount of room the trigger must move before you feel the resistance, this should be kept to a minimum as excessive take up may cause the shooter to flinch as he/she attempts to pull the trigger fast

The Pull:
The resistance to pulling the trigger on a double action guns is caused by a few things: 
1. The geometry of the internal components that must exert mechanical force on the hammer in order to cock and release it.
2. The hammer & trigger return springs which resist the movement and return the parts to their static state.
3. The drag caused by metal to metal contact between the trigger, hammer & sears and also the contact between the hammer/trigger and the frame inside the revolver.
Some pulls will also seem to "stack" which means the felt resistance gets harder as you pull, this is partly caused by the mechanics inside the gun and by the mating surfaces.

The Release or Break: This is the point at which the sear is released from the trigger and the hammer is allowed to fall. The break should be "clean" or without grittiness (is that a word?).
You should not be able to tell when it will break (without practice). The idea is that the pulling (or squeezing) of the trigger should be smooth and easy so that you do not pull the gun off of the target in the sights.

The Over-Travel:
Sometimes a trigger will have movement beyond the necessary travel to operate the sear. This is important as excessive over-travel can cause trouble with follow-up shots. Some guns (like the 1911) can be outfitted with screws in their triggers to stop over-travel. Some gunsmiths install rubber "stops" on the back side of revolver triggers to aid over-travel.

Trigger reset: How far must the trigger move forward to reset the sear. This is determined by the design of the internal components, sometimes there is nothing that can be done to fix it.

While there is some things you can do to improve the trigger by smoothing up the mating surfaces of the trigger and sear, this is not easy and without the correct fixture or training you could make your gun unusable or worse: unsafe. The angles must be kept the same as they were designed and the amount of metal taken off needs to be monitored closely, removing too much metal and the gun may fire from vibration, dropping or ??

I decided to try to clean up the surfaces, lighten up the springs and add trigger & hammer shims.

The trigger shims will provide a "bearing surface" for the hammer and trigger to rub against, this makes the action smoother and prevents the flashing inside frame (left over from the casting or forging process) from interfering with the movement of the trigger and hammer.



I purchased a new trigger/hammer spring kit (Wolff) and a trigger/hammer shim kit from trigger shims.com.

This is what the kit looked like and the gun I will be modifying

 A close up of the parts

The stock hammer spring is set at 14 lbs and the stock trigger return is set at 10 lbs. I chose to use the 9 pound hammer spring and the 8 pound trigger return spring.
First step is dis-assembly, here are two exploded diagrams (click on them for enlarged pictures):


some pics of the sears


 
If you have never taken apart a Ruger Double Action Revolver before, you are in for a surprise, they are by far the easiest gun to dis-assemble/re-assemble.
Before you begin, unload the gun, then check to make sure it is unloaded, finally check to make sure it is unloaded. That is not a typo, way too many accidents happen because people assume a gun is unloaded, check it, then check it again!

The first step in dis-assembly is removing the grips panels with a screw driver
remove the screw, then the grip panels. There will be a thick pin holding the grips on, push it out of its slot and remove the grips by pulling down and away from the butt of the gun. You hopefully will find a small brass pin sitting in a slot in the right side grip panel recess, if not, source a finishing nail, you will need this for the next step. removing the hammer strut:
Cock the hammer and slide the pin into the hole that is now exposed at the bottom of the hammer strut. Next pull the trigger and gently let the hammer fall. The hammer strut and captured spring can now be removed from the grip frame.
Note the orientation of the hammer strut and the saddle, you can reverse the orientation of the strut, some say this provides a better angle, I could not tell the difference on my gun. The less steep angle at the top normally goes towards the muzzle end.
Next you want to remove the hammer, push on the hammer pin (in picture below) while working the hammer and trigger, you have to "jiggle" it a little, but it should come right out.
The next step is removing the trigger guard assembly. There is a spring loaded button on the back of the trigger guard that locks into a recess on the grip frame, see below:
Insert a screw driver or punch into the hole on the back of the grip frame and push it the plunger while prying down at the same time.
Once it is loose, gently remove it from the frame
Next we will install the shims. The pin you see above, directly above the trigger, is the trigger pivot pin. Gently tap the pin part way out so that you have enough gap to install the shims, there are two sizes in the kit, I used the .003, as the .005 would not fit. Use some gun grease or petroleum jelly on the shims, this provides lubricant and helps keep the shims in place. Repeat the process for the other side.

Next we will remove the Trigger return spring. This spring serves double duty as it puts pressure on the trigger and holds the trigger guard in place in the frame. The pin is at the rear of the trigger guard. Simply push the plunger in (to take pressure off) and push out the pin with a punch.
I took the time to clean up the recess where the plunger rides and polish the plunger as well:


Swap the factory spring for the lighter 8 pound one. Reverse the process and we are done with the trigger.
I then carefully "cleaned up" the surface of the trigger sear and polished the cylinder stop. Only remove enough material to alter the surface, you will notice the color will lighten a bit, use 1000 grit paper and go slow.

Then reinstall the trigger guard back into the frame. Be careful to make sure the pawl and hammer transfer bar safety slide into their correct positions, it may take a couple of tries, be patient.
Next Step is to replace the hammer spring. You need to find a piece of wood and drill a 3/8 hole about 1/4" deep, this provides a place to press the hammer strut into so you can relieve the pressure on the spring, the factory one is set at 14 lbs, we are replacing it with a 9 lbs spring. Standard orientation is the less steep angle and the saddle "hoop" faces the front of the gun.
I also polished the head of the hammer strut, this rounded part has to ride metal to metal in a recess on the back of the hammer. A good polish and some grease will allow for smoother operation:

I also polished the hammer pin and the hammer pin hole:

 Then I polished the Hammer Dog and the sear surface on the hammer, again I cannot stress enough, use 1000 grit, light pressure and go slow, rushing and taking too much metal can ruin the part.

Once you have them swapped out, now we need to install the shims on the hammer. These are a bit more difficult. Use some grease to "stick" the shims to the hammer (lining them up with the pin hole) then carefully slide the hammer back into place. You may have to pull the trigger to get the hammer to slide down far enough. use a punch to help line everything up, if you have the shims and the hammer lined up with the holes, go ahead and re-install the hammer pin.
Next step is to re-install the hammer strut. Slide it into the grip frame and cock the hammer, if everything is lined up correctly, the hammer strut saddle will fit snugly into its recess and you will be able to remove the pin that captured the hammer spring.
Finally, re-install your grips (or install a set of Hogues) and test the trigger with some dry-fire practice.


You should see a noticeable difference in the trigger pull. It should be smoother and lighter than before. This should help you keep your sights on target.

I measured the trigger pull after the modifications (and after a few more boxes of ammo and the results averaged just over 8 lbs for DA and 3 1/4 lbs for SA. I must tell you those numbers surprised me as it doesn't feel near that heavy.

if you are interested in more information on performing this kind of work yourself, go to www.sp101trigger.com there is another great tutorial there with pictures. 

Don't be afraid to try this, if you do screw up a part or loose something, Ruger sells factory replacement parts as does Brownells and Midway USA.